feat: adds `replSource` property and command-line option

The `replSource` property specifies the frege source file that you want to
load into the repl. It is excluded in the `fregeCompile` task so that
we don't get two java class files (one from `compileFrege` and one
from the fregeRepl `:l` command) that shadow each other on the classpath.

As a result, we can make interactive changes to the `replSource` file and
use the `:r` reload command to see them.

1 files changed, 505 insertions, 399 deletions

diff --git a/src/functionalTest/java/ch/fhnw/thga/gradleplugins/FregePluginFunctionalTest.java b/src/functionalTest/java/ch/fhnw/thga/gradleplugins/FregePluginFunctionalTest.java
index ad0265b..c1d482f 100644
--- a/src/functionalTest/java/ch/fhnw/thga/gradleplugins/FregePluginFunctionalTest.java
+++ b/src/functionalTest/java/ch/fhnw/thga/gradleplugins/FregePluginFunctionalTest.java
@@ -2,18 +2,19 @@ package ch.fhnw.thga.gradleplugins;
 
 import static ch.fhnw.thga.gradleplugins.FregeExtension.DEFAULT_DOWNLOAD_DIRECTORY;
 import static ch.fhnw.thga.gradleplugins.FregePlugin.COMPILE_FREGE_TASK_NAME;
+import static ch.fhnw.thga.gradleplugins.FregePlugin.DEPS_FREGE_TASK_NAME;
 import static ch.fhnw.thga.gradleplugins.FregePlugin.FREGE_EXTENSION_NAME;
 import static ch.fhnw.thga.gradleplugins.FregePlugin.FREGE_PLUGIN_ID;
-import static ch.fhnw.thga.gradleplugins.FregePlugin.DEPS_FREGE_TASK_NAME;
+import static ch.fhnw.thga.gradleplugins.FregePlugin.REPL_FREGE_TASK_NAME;
 import static ch.fhnw.thga.gradleplugins.FregePlugin.RUN_FREGE_TASK_NAME;
 import static ch.fhnw.thga.gradleplugins.FregePlugin.SETUP_FREGE_TASK_NAME;
-import static ch.fhnw.thga.gradleplugins.FregePlugin.REPL_FREGE_TASK_NAME;
 import static ch.fhnw.thga.gradleplugins.GradleBuildFileConversionTest.createPluginsSection;
 import static org.gradle.testkit.runner.TaskOutcome.FAILED;
 import static org.gradle.testkit.runner.TaskOutcome.FROM_CACHE;
 import static org.gradle.testkit.runner.TaskOutcome.SUCCESS;
 import static org.gradle.testkit.runner.TaskOutcome.UP_TO_DATE;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.io.BufferedWriter;
@@ -44,407 +45,512 @@ import ch.fhnw.thga.gradleplugins.internal.DependencyFregeTask;
 
 @TestInstance(Lifecycle.PER_CLASS)
 public class FregePluginFunctionalTest {
-        private static final String NEW_LINE = System.lineSeparator();
-        private static final String SIMPLE_FREGE_CODE = String.join(NEW_LINE, "module ch.fhnw.thga.Completion where",
-                        NEW_LINE, NEW_LINE, "  complete :: Int -> (Int, String)", NEW_LINE,
-                        "  complete i = (i, \"Frege rocks\")",
-                        NEW_LINE);
-
-        private static FregeDTOBuilder fregeBuilder;
-
-        @TempDir
-        File testProjectDir;
-        private File buildFile;
-        private File settingsFile;
-        private Project project;
-
-        private void writeFile(File destination, String content, boolean append) throws IOException {
-                try (BufferedWriter output = new BufferedWriter(new FileWriter(destination, append))) {
-                        output.write(content);
-                }
-        }
-
-        private void writeToFile(File destination, String content) throws IOException {
-                writeFile(destination, content, false);
-        }
-
-        private void appendToFile(File destination, String content) throws IOException {
-                writeFile(destination, "\n" + content, true);
-        }
-
-        private static String createFregeSection(FregeDTO fregeDTO) {
-                return String.format("%s {\n  %s\n}", FREGE_EXTENSION_NAME, fregeDTO.toBuildFile());
-        }
-
-        private BuildResult runGradleTask(String... taskName) {
-                return GradleRunner.create().withProjectDir(testProjectDir).withPluginClasspath()
-                                .withArguments(taskName)
-                                .build();
-        }
-
-        private BuildResult runAndFailGradleTask(String taskName, String... args) {
-                return GradleRunner.create().withProjectDir(testProjectDir).withPluginClasspath()
-                                .withArguments(taskName)
-                                .buildAndFail();
-        }
-
-        private void setupDefaultFregeProjectStructure(String fregeCode, String fregeFileName, String buildFileConfig)
-                        throws Exception {
-                Files.createDirectories(testProjectDir.toPath().resolve(Paths.get("src", "main", "frege")));
-                File fregeFile = testProjectDir.toPath().resolve(Paths.get("src", "main", "frege", fregeFileName))
-                                .toFile();
-                writeToFile(fregeFile, fregeCode);
-                appendToFile(buildFile, buildFileConfig);
-        }
-
-        @BeforeAll
-        void beforeAll() throws Exception {
-                settingsFile = new File(testProjectDir, "settings.gradle");
-                writeToFile(settingsFile, "rootProject.name='frege-plugin'");
-                project = ProjectBuilder.builder().withProjectDir(testProjectDir).build();
-                project.getPluginManager().apply(FREGE_PLUGIN_ID);
-
+    private static final String NEW_LINE = System.lineSeparator();
+    private static final String SIMPLE_FREGE_CODE = String.join(NEW_LINE, "module ch.fhnw.thga.Completion where",
+                    NEW_LINE, NEW_LINE, "  complete :: Int -> (Int, String)", NEW_LINE,
+                    "  complete i = (i, \"Frege rocks\")",
+                    NEW_LINE);
+
+    private static FregeDTOBuilder fregeBuilder;
+
+    @TempDir
+    File testProjectDir;
+    private File buildFile;
+    private File settingsFile;
+    private Project project;
+
+    private void writeFile(File destination, String content, boolean append) throws IOException {
+            try (BufferedWriter output = new BufferedWriter(new FileWriter(destination, append))) {
+                    output.write(content);
+            }
+    }
+
+    private void writeToFile(File destination, String content) throws IOException {
+            writeFile(destination, content, false);
+    }
+
+    private void appendToFile(File destination, String content) throws IOException {
+            writeFile(destination, System.lineSeparator() + content, true);
+    }
+
+    private static String createFregeSection(FregeDTO fregeDTO) {
+            return String.format(
+                "%s {%s  %s%s}",
+                FREGE_EXTENSION_NAME,
+                System.lineSeparator(),
+                fregeDTO.toBuildFile(),
+                System.lineSeparator());
+    }
+
+    private BuildResult runGradleTask(String... taskName) {
+            return GradleRunner.create().withProjectDir(testProjectDir).withPluginClasspath()
+                            .withArguments(taskName)
+                            .build();
+    }
+
+    private BuildResult runAndFailGradleTask(String taskName, String... args) {
+            return GradleRunner.create().withProjectDir(testProjectDir).withPluginClasspath()
+                            .withArguments(taskName)
+                            .buildAndFail();
+    }
+
+    private void setupDefaultFregeProjectStructure(String fregeCode, String fregeFileName, String buildFileConfig)
+                    throws Exception {
+            Files.createDirectories(testProjectDir.toPath().resolve(Paths.get("src", "main", "frege")));
+            File fregeFile = testProjectDir.toPath().resolve(Paths.get("src", "main", "frege", fregeFileName))
+                            .toFile();
+            writeToFile(fregeFile, fregeCode);
+            appendToFile(buildFile, buildFileConfig);
+    }
+
+    @BeforeAll
+    void beforeAll() throws Exception {
+            settingsFile = new File(testProjectDir, "settings.gradle");
+            writeToFile(settingsFile, "rootProject.name='frege-plugin'");
+            project = ProjectBuilder.builder().withProjectDir(testProjectDir).build();
+            project.getPluginManager().apply(FREGE_PLUGIN_ID);
+
+    }
+
+    @BeforeEach
+    void setup() throws Exception {
+            buildFile = new File(testProjectDir, "build.gradle");
+            writeToFile(buildFile, createPluginsSection(Stream.of(FREGE_PLUGIN_ID)));
+            fregeBuilder = FregeDTOBuilder.getInstance();
+    }
+
+    @AfterEach
+    void cleanup() {
+            testProjectDir.delete();
+    }
+
+    @Nested
+    @TestInstance(Lifecycle.PER_CLASS)
+    @IndicativeSentencesGeneration(separator = " -> ", generator = DisplayNameGenerator.ReplaceUnderscores.class)
+    class Setup_frege_task_works {
+
+            @Test
+            void given_minimal_build_file_config() throws Exception {
+                    String minimalBuildFileConfig = createFregeSection(
+                                    fregeBuilder.version("'3.25.84'").release("'3.25alpha'").build());
+                    appendToFile(buildFile, minimalBuildFileConfig);
+
+                    BuildResult result = runGradleTask(SETUP_FREGE_TASK_NAME);
+
+                    assertTrue(project.getTasks().getByName(SETUP_FREGE_TASK_NAME) instanceof SetupFregeTask);
+                    assertEquals(SUCCESS, result.task(":" + SETUP_FREGE_TASK_NAME).getOutcome());
+                    assertTrue(testProjectDir.toPath()
+                                    .resolve(Paths.get(DEFAULT_DOWNLOAD_DIRECTORY, "frege3.25.84.jar"))
+                                    .toFile().exists());
+            }
+
+            @Test
+            void given_custom_frege_compiler_download_directory_in_build_file_config() throws Exception {
+                    String buildFileConfigWithCustomDownloadDir = createFregeSection(fregeBuilder
+                                    .version("'3.25.84'")
+                                    .release("'3.25alpha'")
+                                    .compilerDownloadDir("layout.projectDirectory.dir('dist')").build());
+                    appendToFile(buildFile, buildFileConfigWithCustomDownloadDir);
+
+                    BuildResult result = runGradleTask(SETUP_FREGE_TASK_NAME);
+
+                    assertTrue(project.getTasks().getByName(SETUP_FREGE_TASK_NAME) instanceof SetupFregeTask);
+                    assertEquals(SUCCESS, result.task(":" + SETUP_FREGE_TASK_NAME).getOutcome());
+                    assertTrue(testProjectDir.toPath().resolve(Paths.get("dist", "frege3.25.84.jar")).toFile()
+                                    .exists());
+            }
+    }
+
+    @Nested
+    @TestInstance(Lifecycle.PER_CLASS)
+    @IndicativeSentencesGeneration(separator = " -> ", generator = DisplayNameGenerator.ReplaceUnderscores.class)
+    class Compile_frege_task_works {
+
+            @Test
+            void given_frege_code_in_default_source_dir_and_minimal_build_file_config() throws Exception {
+                    String completionFr = "Completion.fr";
+                    String minimalBuildFileConfig = createFregeSection(
+                                    fregeBuilder.version("'3.25.84'").release("'3.25alpha'").build());
+                    setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr, minimalBuildFileConfig);
+
+                    BuildResult result = runGradleTask(COMPILE_FREGE_TASK_NAME);
+
+                    assertTrue(project.getTasks().getByName(COMPILE_FREGE_TASK_NAME) instanceof CompileFregeTask);
+                    assertEquals(SUCCESS, result.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
+                    assertTrue(new File(
+                                    testProjectDir.getAbsolutePath()
+                                                    + "/build/classes/main/frege/ch/fhnw/thga/Completion.java")
+                                                                    .exists());
+                    assertTrue(new File(
+                                    testProjectDir.getAbsolutePath()
+                                                    + "/build/classes/main/frege/ch/fhnw/thga/Completion.class")
+                                                                    .exists());
+            }
+
+            @Test
+            void given_frege_code_and_many_compiler_flags() throws Exception {
+                    String completionFr = "Completion.fr";
+                    String buildConfigWithCompilerFlags = createFregeSection(fregeBuilder.version("'3.25.84'")
+                                    .release("'3.25alpha'").compilerFlags("['-v', '-make', '-O', '-hints']")
+                                    .build());
+                    setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr,
+                                    buildConfigWithCompilerFlags);
+
+                    BuildResult result = runGradleTask(COMPILE_FREGE_TASK_NAME);
+
+                    assertTrue(project.getTasks().getByName(COMPILE_FREGE_TASK_NAME) instanceof CompileFregeTask);
+                    assertEquals(SUCCESS, result.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
+                    assertTrue(new File(
+                                    testProjectDir.getAbsolutePath()
+                                                    + "/build/classes/main/frege/ch/fhnw/thga/Completion.java")
+                                                                    .exists());
+                    assertTrue(new File(
+                                    testProjectDir.getAbsolutePath()
+                                                    + "/build/classes/main/frege/ch/fhnw/thga/Completion.class")
+                                                                    .exists());
+            }
+
+            @Test
+            void given_frege_code_in_custom_source_dir_and_custom_output_dir_and_minimal_build_file_config()
+                            throws Exception {
+                    Path customMainSourceDir = testProjectDir.toPath().resolve(Paths.get("src", "frege"));
+                    Files.createDirectories(customMainSourceDir);
+                    File completionFr = customMainSourceDir.resolve("Completion.fr").toFile();
+                    writeToFile(completionFr, SIMPLE_FREGE_CODE);
+                    String minimalBuildFileConfig = createFregeSection(
+                                    fregeBuilder.version("'3.25.84'").release("'3.25alpha'")
+                                                    .mainSourceDir("layout.projectDirectory.dir('src/frege')")
+                                                    .outputDir("layout.buildDirectory.dir('frege')").build());
+                    appendToFile(buildFile, minimalBuildFileConfig);
+
+                    BuildResult result = runGradleTask(COMPILE_FREGE_TASK_NAME);
+
+                    assertTrue(project.getTasks().getByName(COMPILE_FREGE_TASK_NAME) instanceof CompileFregeTask);
+                    assertEquals(SUCCESS, result.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
+                    assertTrue(
+                                    new File(testProjectDir.getAbsolutePath()
+                                                    + "/build/frege/ch/fhnw/thga/Completion.java").exists());
+                    assertTrue(
+                                    new File(testProjectDir.getAbsolutePath()
+                                                    + "/build/frege/ch/fhnw/thga/Completion.class").exists());
+            }
+
+            @Test
+            void and_is_up_to_date_given_no_code_changes() throws Exception {
+                    String completionFr = "Completion.fr";
+                    String minimalBuildFileConfig = createFregeSection(
+                                    fregeBuilder.version("'3.25.84'").release("'3.25alpha'").build());
+                    setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr, minimalBuildFileConfig);
+
+                    BuildResult first = runGradleTask(COMPILE_FREGE_TASK_NAME);
+                    assertEquals(SUCCESS, first.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
+
+                    BuildResult second = runGradleTask(COMPILE_FREGE_TASK_NAME);
+                    assertEquals(UP_TO_DATE, second.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
+            }
+
+            @Test
+            void and_is_cached_given_cache_hit() throws Exception {
+                    String completionFr = "Completion.fr";
+                    String minimalBuildFileConfig = createFregeSection(
+                                    fregeBuilder.version("'3.25.84'").release("'3.25alpha'").build());
+                    setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr, minimalBuildFileConfig);
+
+                    BuildResult first = runGradleTask(COMPILE_FREGE_TASK_NAME, "--build-cache");
+                    assertEquals(SUCCESS, first.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
+
+                    String codeChange = String.join(NEW_LINE, "module ch.fhnw.thga.Completion where", NEW_LINE,
+                                    NEW_LINE,
+                                    "  frob :: Int -> (Int, String)", NEW_LINE, "  frob i = (i, \"Frege rocks\")",
+                                    NEW_LINE);
+                    setupDefaultFregeProjectStructure(codeChange, completionFr, "");
+
+                    BuildResult second = runGradleTask(COMPILE_FREGE_TASK_NAME, "--build-cache");
+                    assertEquals(SUCCESS, second.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
+
+                    setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr, "");
+                    BuildResult third = runGradleTask(COMPILE_FREGE_TASK_NAME, "--build-cache");
+                    assertEquals(FROM_CACHE, third.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
+            }
+
+            @Test
+            void given_two_dependent_frege_files_in_default_source_dir_and_minimal_build_file_config()
+                            throws Exception {
+                    String completionFr = "Completion.fr";
+                    String frobFr = "Frob.fr";
+                    String frobCode = String.join(NEW_LINE, "module ch.fhnw.thga.Frob where", NEW_LINE, NEW_LINE,
+                                    "import ch.fhnw.thga.Completion (complete)", NEW_LINE,
+                                    "frob i = complete $ i + i", NEW_LINE);
+
+                    String minimalBuildFileConfig = createFregeSection(
+                                    fregeBuilder.version("'3.25.84'").release("'3.25alpha'").build());
+                    setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr, minimalBuildFileConfig);
+                    setupDefaultFregeProjectStructure(frobCode, frobFr, "");
+
+                    BuildResult result = runGradleTask(COMPILE_FREGE_TASK_NAME);
+
+                    assertTrue(project.getTasks().getByName(COMPILE_FREGE_TASK_NAME) instanceof CompileFregeTask);
+                    assertEquals(SUCCESS, result.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
+                    assertTrue(new File(
+                                    testProjectDir.getAbsolutePath()
+                                                    + "/build/classes/main/frege/ch/fhnw/thga/Completion.java")
+                                                                    .exists());
+                    assertTrue(new File(
+                                    testProjectDir.getAbsolutePath()
+                                                    + "/build/classes/main/frege/ch/fhnw/thga/Completion.class")
+                                                                    .exists());
+                    assertTrue(new File(testProjectDir.getAbsolutePath()
+                                    + "/build/classes/main/frege/ch/fhnw/thga/Frob.java")
+                                                    .exists());
+                    assertTrue(new File(testProjectDir.getAbsolutePath()
+                                    + "/build/classes/main/frege/ch/fhnw/thga/Frob.class")
+                                                    .exists());
+            }
+    }
+
+    @Nested
+    @TestInstance(Lifecycle.PER_CLASS)
+    @IndicativeSentencesGeneration(separator = " -> ", generator = DisplayNameGenerator.ReplaceUnderscores.class)
+    class Compile_frege_task_fails {
+            @Test
+            void given_frege_code_and_illegal_compiler_flags() throws Exception {
+                    String completionFr = "Completion.fr";
+                    String buildConfigWithIllegalCompilerFlags = createFregeSection(fregeBuilder
+                                    .version("'3.25.84'")
+                                    .release("'3.25alpha'").compilerFlags("['-make', '-bla']").build());
+                    setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr,
+                                    buildConfigWithIllegalCompilerFlags);
+
+                    BuildResult result = runAndFailGradleTask(COMPILE_FREGE_TASK_NAME);
+
+                    assertTrue(project.getTasks().getByName(COMPILE_FREGE_TASK_NAME) instanceof CompileFregeTask);
+                    assertEquals(FAILED, result.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
+            }
+
+            @Test
+            void given_two_dependent_frege_files_in_default_source_dir_and_without_make_compiler_flag()
+                            throws Exception {
+                    String completionFr = "Completion.fr";
+                    String frobFr = "Frob.fr";
+                    String frobCode = String.join(NEW_LINE, "module ch.fhnw.thga.Frob where", NEW_LINE, NEW_LINE,
+                                    "import ch.fhnw.thga.Completion (complete)", NEW_LINE,
+                                    "frob i = complete $ i + i", NEW_LINE);
+
+                    String minimalBuildFileConfigWithoutMake = createFregeSection(
+                                    fregeBuilder.version("'3.25.84'").release("'3.25alpha'").compilerFlags("['-v']")
+                                                    .build());
+                    setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr,
+                                    minimalBuildFileConfigWithoutMake);
+                    setupDefaultFregeProjectStructure(frobCode, frobFr, "");
+
+                    BuildResult result = runAndFailGradleTask(COMPILE_FREGE_TASK_NAME);
+
+                    assertTrue(project.getTasks().getByName(COMPILE_FREGE_TASK_NAME) instanceof CompileFregeTask);
+                    assertEquals(FAILED, result.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
+            }
+    }
+
+    @Nested
+    @TestInstance(Lifecycle.PER_CLASS)
+    @IndicativeSentencesGeneration(separator = " -> ", generator = DisplayNameGenerator.ReplaceUnderscores.class)
+    class Run_frege_task_works {
+            @Test
+            void given_frege_file_with_main_function_and_main_module_config() throws Exception {
+                    String fregeCode = String.join(NEW_LINE, "module ch.fhnw.thga.Main where", NEW_LINE, NEW_LINE,
+                                    "  main = do", NEW_LINE, "    println \"Frege rocks\"", NEW_LINE);
+                    String mainFr = "Main.fr";
+                    String buildFileConfig = createFregeSection(
+                                    fregeBuilder.version("'3.25.84'").release("'3.25alpha'")
+                                                    .mainModule("'ch.fhnw.thga.Main'").build());
+                    setupDefaultFregeProjectStructure(fregeCode, mainFr, buildFileConfig);
+
+                    BuildResult result = runGradleTask(RUN_FREGE_TASK_NAME);
+                    assertTrue(project.getTasks().getByName(RUN_FREGE_TASK_NAME) instanceof RunFregeTask);
+                    assertEquals(SUCCESS, result.task(":" + RUN_FREGE_TASK_NAME).getOutcome());
+                    assertTrue(result.getOutput().contains("Frege rocks"));
+            }
+
+            @Test
+            void given_frege_file_without_main_function() throws Exception {
+                    String completionFr = "Completion.fr";
+                    String buildFileConfig = createFregeSection(
+                                    fregeBuilder.version("'3.25.84'").release("'3.25alpha'")
+                                                    .mainModule("'ch.fhnw.thga.Completion'").build());
+                    setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr, buildFileConfig);
+
+                    BuildResult result = runAndFailGradleTask(RUN_FREGE_TASK_NAME);
+                    assertTrue(project.getTasks().getByName(RUN_FREGE_TASK_NAME) instanceof RunFregeTask);
+                    assertEquals(FAILED, result.task(":" + RUN_FREGE_TASK_NAME).getOutcome());
+                    assertTrue(result.getOutput().contains("Main method not found"));
+            }
+
+            @Test
+            void given_frege_file_with_main_function_and_main_module_command_line_option() throws Exception {
+                    String fregeCode = String.join(NEW_LINE, "module ch.fhnw.thga.Main where", NEW_LINE, NEW_LINE,
+                                    "  main = do", NEW_LINE, "    println \"Frege rocks\"", NEW_LINE);
+                    String mainFr = "Main.fr";
+                    String buildFileConfig = createFregeSection(
+                                    fregeBuilder.version("'3.25.84'").release("'3.25alpha'").build());
+                    setupDefaultFregeProjectStructure(fregeCode, mainFr, buildFileConfig);
+
+                    BuildResult result = runGradleTask(RUN_FREGE_TASK_NAME, "--mainModule=ch.fhnw.thga.Main");
+                    assertTrue(project.getTasks().getByName(RUN_FREGE_TASK_NAME) instanceof RunFregeTask);
+                    assertEquals(SUCCESS, result.task(":" + RUN_FREGE_TASK_NAME).getOutcome());
+                    assertTrue(result.getOutput().contains("Frege rocks"));
+            }
+    }
+
+    @Nested
+    @TestInstance(Lifecycle.PER_CLASS)
+    @IndicativeSentencesGeneration(
+        separator = " -> ",
+        generator = DisplayNameGenerator.ReplaceUnderscores.class)
+    class Deps_frege_task_works {
+        @Test
+        void given_minimal_build_file_config() throws Exception {
+            String completionFr           = "Completion.fr";
+            String minimalBuildFileConfig = createFregeSection(
+                fregeBuilder
+                .version("'3.25.84'")
+                .release("'3.25alpha'")
+                .build());
+            setupDefaultFregeProjectStructure(
+                SIMPLE_FREGE_CODE,
+                completionFr,
+                minimalBuildFileConfig);
+
+            BuildResult result = runGradleTask(
+                DEPS_FREGE_TASK_NAME,
+                "-q",
+                String.format("--replSource=%s", completionFr));
+
+            assertTrue(
+                project.getTasks().getByName(DEPS_FREGE_TASK_NAME)
+                instanceof DependencyFregeTask);
+            assertEquals(SUCCESS, result.task(":" + DEPS_FREGE_TASK_NAME).getOutcome());
+            assertTrue(result.getOutput().contains("frege3.25.84.jar"));
+            assertFalse(result.getOutput().contains("Completion.java"));
+            assertFalse(
+                testProjectDir
+                .toPath()
+                .resolve("/build/classes/main/frege/ch/fhnw/thga/Completion.java").toFile()
+                .exists());
         }
 
-        @BeforeEach
-        void setup() throws Exception {
-                buildFile = new File(testProjectDir, "build.gradle");
-                writeToFile(buildFile, createPluginsSection(Stream.of(FREGE_PLUGIN_ID)));
-                fregeBuilder = FregeDTOBuilder.getInstance();
-        }
-
-        @AfterEach
-        void cleanup() {
-                testProjectDir.delete();
-        }
 
-        @Nested
-        @TestInstance(Lifecycle.PER_CLASS)
-        @IndicativeSentencesGeneration(separator = " -> ", generator = DisplayNameGenerator.ReplaceUnderscores.class)
-        class Setup_frege_task_works {
-
-                @Test
-                void given_minimal_build_file_config() throws Exception {
-                        String minimalBuildFileConfig = createFregeSection(
-                                        fregeBuilder.version("'3.25.84'").release("'3.25alpha'").build());
-                        appendToFile(buildFile, minimalBuildFileConfig);
-
-                        BuildResult result = runGradleTask(SETUP_FREGE_TASK_NAME);
-
-                        assertTrue(project.getTasks().getByName(SETUP_FREGE_TASK_NAME) instanceof SetupFregeTask);
-                        assertEquals(SUCCESS, result.task(":" + SETUP_FREGE_TASK_NAME).getOutcome());
-                        assertTrue(testProjectDir.toPath()
-                                        .resolve(Paths.get(DEFAULT_DOWNLOAD_DIRECTORY, "frege3.25.84.jar"))
-                                        .toFile().exists());
-                }
-
-                @Test
-                void given_custom_frege_compiler_download_directory_in_build_file_config() throws Exception {
-                        String buildFileConfigWithCustomDownloadDir = createFregeSection(fregeBuilder
-                                        .version("'3.25.84'")
-                                        .release("'3.25alpha'")
-                                        .compilerDownloadDir("layout.projectDirectory.dir('dist')").build());
-                        appendToFile(buildFile, buildFileConfigWithCustomDownloadDir);
-
-                        BuildResult result = runGradleTask(SETUP_FREGE_TASK_NAME);
-
-                        assertTrue(project.getTasks().getByName(SETUP_FREGE_TASK_NAME) instanceof SetupFregeTask);
-                        assertEquals(SUCCESS, result.task(":" + SETUP_FREGE_TASK_NAME).getOutcome());
-                        assertTrue(testProjectDir.toPath().resolve(Paths.get("dist", "frege3.25.84.jar")).toFile()
-                                        .exists());
-                }
+        @Test
+        void given_build_file_config_with_dependencies() throws Exception {
+            String completionFr           = "Completion.fr";
+            String minimalBuildFileConfig = createFregeSection(
+                fregeBuilder
+                .version("'3.25.84'")
+                .release("'3.25alpha'")
+                .build());
+            setupDefaultFregeProjectStructure(
+                SIMPLE_FREGE_CODE,
+                completionFr,
+                minimalBuildFileConfig);
+            appendToFile(
+                buildFile,
+                String.join(
+                    System.lineSeparator(),
+                    "repositories {",
+                      "mavenCentral()",
+                    "}"));
+            appendToFile(
+                buildFile,
+                String.join(
+                    System.lineSeparator(),
+                    "dependencies {",
+                      "implementation group: 'org.json', name: 'json', version: '20211205'",
+                    "}"));
+
+            BuildResult result = runGradleTask(
+                DEPS_FREGE_TASK_NAME,
+                "-q",
+                String.format("--replSource=%s", completionFr));
+
+            assertTrue(
+                project.getTasks().getByName(DEPS_FREGE_TASK_NAME)
+                instanceof DependencyFregeTask);
+            assertEquals(SUCCESS, result.task(":" + DEPS_FREGE_TASK_NAME).getOutcome());
+            assertTrue(result.getOutput().contains("frege3.25.84.jar"));
+            assertTrue(result.getOutput().contains("org.json"));
+            assertFalse(result.getOutput().contains("Completion.java"));
+            assertFalse(
+                testProjectDir
+                .toPath()
+                .resolve("/build/classes/main/frege/ch/fhnw/thga/Completion.java").toFile()
+                .exists());
         }
-
-        @Nested
-        @TestInstance(Lifecycle.PER_CLASS)
-        @IndicativeSentencesGeneration(separator = " -> ", generator = DisplayNameGenerator.ReplaceUnderscores.class)
-        class Compile_frege_task_works {
-
-                @Test
-                void given_frege_code_in_default_source_dir_and_minimal_build_file_config() throws Exception {
-                        String completionFr = "Completion.fr";
-                        String minimalBuildFileConfig = createFregeSection(
-                                        fregeBuilder.version("'3.25.84'").release("'3.25alpha'").build());
-                        setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr, minimalBuildFileConfig);
-
-                        BuildResult result = runGradleTask(COMPILE_FREGE_TASK_NAME);
-
-                        assertTrue(project.getTasks().getByName(COMPILE_FREGE_TASK_NAME) instanceof CompileFregeTask);
-                        assertEquals(SUCCESS, result.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
-                        assertTrue(new File(
-                                        testProjectDir.getAbsolutePath()
-                                                        + "/build/classes/main/frege/ch/fhnw/thga/Completion.java")
-                                                                        .exists());
-                        assertTrue(new File(
-                                        testProjectDir.getAbsolutePath()
-                                                        + "/build/classes/main/frege/ch/fhnw/thga/Completion.class")
-                                                                        .exists());
-                }
-
-                @Test
-                void given_frege_code_and_many_compiler_flags() throws Exception {
-                        String completionFr = "Completion.fr";
-                        String buildConfigWithCompilerFlags = createFregeSection(fregeBuilder.version("'3.25.84'")
-                                        .release("'3.25alpha'").compilerFlags("['-v', '-make', '-O', '-hints']")
-                                        .build());
-                        setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr,
-                                        buildConfigWithCompilerFlags);
-
-                        BuildResult result = runGradleTask(COMPILE_FREGE_TASK_NAME);
-
-                        assertTrue(project.getTasks().getByName(COMPILE_FREGE_TASK_NAME) instanceof CompileFregeTask);
-                        assertEquals(SUCCESS, result.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
-                        assertTrue(new File(
-                                        testProjectDir.getAbsolutePath()
-                                                        + "/build/classes/main/frege/ch/fhnw/thga/Completion.java")
-                                                                        .exists());
-                        assertTrue(new File(
-                                        testProjectDir.getAbsolutePath()
-                                                        + "/build/classes/main/frege/ch/fhnw/thga/Completion.class")
-                                                                        .exists());
-                }
-
-                @Test
-                void given_frege_code_in_custom_source_dir_and_custom_output_dir_and_minimal_build_file_config()
-                                throws Exception {
-                        Path customMainSourceDir = testProjectDir.toPath().resolve(Paths.get("src", "frege"));
-                        Files.createDirectories(customMainSourceDir);
-                        File completionFr = customMainSourceDir.resolve("Completion.fr").toFile();
-                        writeToFile(completionFr, SIMPLE_FREGE_CODE);
-                        String minimalBuildFileConfig = createFregeSection(
-                                        fregeBuilder.version("'3.25.84'").release("'3.25alpha'")
-                                                        .mainSourceDir("layout.projectDirectory.dir('src/frege')")
-                                                        .outputDir("layout.buildDirectory.dir('frege')").build());
-                        appendToFile(buildFile, minimalBuildFileConfig);
-
-                        BuildResult result = runGradleTask(COMPILE_FREGE_TASK_NAME);
-
-                        assertTrue(project.getTasks().getByName(COMPILE_FREGE_TASK_NAME) instanceof CompileFregeTask);
-                        assertEquals(SUCCESS, result.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
-                        assertTrue(
-                                        new File(testProjectDir.getAbsolutePath()
-                                                        + "/build/frege/ch/fhnw/thga/Completion.java").exists());
-                        assertTrue(
-                                        new File(testProjectDir.getAbsolutePath()
-                                                        + "/build/frege/ch/fhnw/thga/Completion.class").exists());
-                }
-
-                @Test
-                void and_is_up_to_date_given_no_code_changes() throws Exception {
-                        String completionFr = "Completion.fr";
-                        String minimalBuildFileConfig = createFregeSection(
-                                        fregeBuilder.version("'3.25.84'").release("'3.25alpha'").build());
-                        setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr, minimalBuildFileConfig);
-
-                        BuildResult first = runGradleTask(COMPILE_FREGE_TASK_NAME);
-                        assertEquals(SUCCESS, first.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
-
-                        BuildResult second = runGradleTask(COMPILE_FREGE_TASK_NAME);
-                        assertEquals(UP_TO_DATE, second.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
-                }
-
-                @Test
-                void and_is_cached_given_cache_hit() throws Exception {
-                        String completionFr = "Completion.fr";
-                        String minimalBuildFileConfig = createFregeSection(
-                                        fregeBuilder.version("'3.25.84'").release("'3.25alpha'").build());
-                        setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr, minimalBuildFileConfig);
-
-                        BuildResult first = runGradleTask(COMPILE_FREGE_TASK_NAME, "--build-cache");
-                        assertEquals(SUCCESS, first.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
-
-                        String codeChange = String.join(NEW_LINE, "module ch.fhnw.thga.Completion where", NEW_LINE,
-                                        NEW_LINE,
-                                        "  frob :: Int -> (Int, String)", NEW_LINE, "  frob i = (i, \"Frege rocks\")",
-                                        NEW_LINE);
-                        setupDefaultFregeProjectStructure(codeChange, completionFr, "");
-
-                        BuildResult second = runGradleTask(COMPILE_FREGE_TASK_NAME, "--build-cache");
-                        assertEquals(SUCCESS, second.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
-
-                        setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr, "");
-                        BuildResult third = runGradleTask(COMPILE_FREGE_TASK_NAME, "--build-cache");
-                        assertEquals(FROM_CACHE, third.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
-                }
-
-                @Test
-                void given_two_dependent_frege_files_in_default_source_dir_and_minimal_build_file_config()
-                                throws Exception {
-                        String completionFr = "Completion.fr";
-                        String frobFr = "Frob.fr";
-                        String frobCode = String.join(NEW_LINE, "module ch.fhnw.thga.Frob where", NEW_LINE, NEW_LINE,
-                                        "import ch.fhnw.thga.Completion (complete)", NEW_LINE,
-                                        "frob i = complete $ i + i", NEW_LINE);
-
-                        String minimalBuildFileConfig = createFregeSection(
-                                        fregeBuilder.version("'3.25.84'").release("'3.25alpha'").build());
-                        setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr, minimalBuildFileConfig);
-                        setupDefaultFregeProjectStructure(frobCode, frobFr, "");
-
-                        BuildResult result = runGradleTask(COMPILE_FREGE_TASK_NAME);
-
-                        assertTrue(project.getTasks().getByName(COMPILE_FREGE_TASK_NAME) instanceof CompileFregeTask);
-                        assertEquals(SUCCESS, result.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
-                        assertTrue(new File(
-                                        testProjectDir.getAbsolutePath()
-                                                        + "/build/classes/main/frege/ch/fhnw/thga/Completion.java")
-                                                                        .exists());
-                        assertTrue(new File(
-                                        testProjectDir.getAbsolutePath()
-                                                        + "/build/classes/main/frege/ch/fhnw/thga/Completion.class")
-                                                                        .exists());
-                        assertTrue(new File(testProjectDir.getAbsolutePath()
-                                        + "/build/classes/main/frege/ch/fhnw/thga/Frob.java")
-                                                        .exists());
-                        assertTrue(new File(testProjectDir.getAbsolutePath()
-                                        + "/build/classes/main/frege/ch/fhnw/thga/Frob.class")
-                                                        .exists());
-                }
+    }
+
+    @Nested
+    @TestInstance(Lifecycle.PER_CLASS)
+    @IndicativeSentencesGeneration(
+        separator = " -> ",
+        generator = DisplayNameGenerator.ReplaceUnderscores.class)
+    class Repl_frege_task_works
+    {
+        @Test
+        void given_minimal_build_file_config_with_replModule() throws Exception
+        {
+            String completionFr            = "Completion.fr";
+            String minimalReplModuleConfig = createFregeSection(
+                fregeBuilder
+                .version("'3.25.84'")
+                .release("'3.25alpha'")
+                .replModule(String.format("'%s'", completionFr))
+                .build());
+            setupDefaultFregeProjectStructure(
+                SIMPLE_FREGE_CODE,
+                completionFr,
+                minimalReplModuleConfig);
+
+            BuildResult result = runGradleTask(REPL_FREGE_TASK_NAME);
+
+            assertTrue(
+                project.getTasks().getByName(REPL_FREGE_TASK_NAME)
+                instanceof ReplFregeTask);
+            assertEquals(SUCCESS, result.task(":" + REPL_FREGE_TASK_NAME).getOutcome());
+            assertTrue(result.getOutput().contains("java -cp"));
+            assertTrue(result.getOutput().contains("frege3.25.84.jar"));
+            assertFalse(result.getOutput().contains("Completion.java"));
+            assertFalse(
+                testProjectDir
+                .toPath()
+                .resolve("/build/classes/main/frege/ch/fhnw/thga/Completion.java").toFile()
+                .exists());
         }
-
-        @Nested
-        @TestInstance(Lifecycle.PER_CLASS)
-        @IndicativeSentencesGeneration(separator = " -> ", generator = DisplayNameGenerator.ReplaceUnderscores.class)
-        class Compile_frege_task_fails {
-                @Test
-                void given_frege_code_and_illegal_compiler_flags() throws Exception {
-                        String completionFr = "Completion.fr";
-                        String buildConfigWithIllegalCompilerFlags = createFregeSection(fregeBuilder
-                                        .version("'3.25.84'")
-                                        .release("'3.25alpha'").compilerFlags("['-make', '-bla']").build());
-                        setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr,
-                                        buildConfigWithIllegalCompilerFlags);
-
-                        BuildResult result = runAndFailGradleTask(COMPILE_FREGE_TASK_NAME);
-
-                        assertTrue(project.getTasks().getByName(COMPILE_FREGE_TASK_NAME) instanceof CompileFregeTask);
-                        assertEquals(FAILED, result.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
-                }
-
-                @Test
-                void given_two_dependent_frege_files_in_default_source_dir_and_without_make_compiler_flag()
-                                throws Exception {
-                        String completionFr = "Completion.fr";
-                        String frobFr = "Frob.fr";
-                        String frobCode = String.join(NEW_LINE, "module ch.fhnw.thga.Frob where", NEW_LINE, NEW_LINE,
-                                        "import ch.fhnw.thga.Completion (complete)", NEW_LINE,
-                                        "frob i = complete $ i + i", NEW_LINE);
-
-                        String minimalBuildFileConfigWithoutMake = createFregeSection(
-                                        fregeBuilder.version("'3.25.84'").release("'3.25alpha'").compilerFlags("['-v']")
-                                                        .build());
-                        setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr,
-                                        minimalBuildFileConfigWithoutMake);
-                        setupDefaultFregeProjectStructure(frobCode, frobFr, "");
-
-                        BuildResult result = runAndFailGradleTask(COMPILE_FREGE_TASK_NAME);
-
-                        assertTrue(project.getTasks().getByName(COMPILE_FREGE_TASK_NAME) instanceof CompileFregeTask);
-                        assertEquals(FAILED, result.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
-                }
-        }
-
-        @Nested
-        @TestInstance(Lifecycle.PER_CLASS)
-        @IndicativeSentencesGeneration(separator = " -> ", generator = DisplayNameGenerator.ReplaceUnderscores.class)
-        class Run_frege_task_works {
-                @Test
-                void given_frege_file_with_main_function_and_main_module_config() throws Exception {
-                        String fregeCode = String.join(NEW_LINE, "module ch.fhnw.thga.Main where", NEW_LINE, NEW_LINE,
-                                        "  main = do", NEW_LINE, "    println \"Frege rocks\"", NEW_LINE);
-                        String mainFr = "Main.fr";
-                        String buildFileConfig = createFregeSection(
-                                        fregeBuilder.version("'3.25.84'").release("'3.25alpha'")
-                                                        .mainModule("'ch.fhnw.thga.Main'").build());
-                        setupDefaultFregeProjectStructure(fregeCode, mainFr, buildFileConfig);
-
-                        BuildResult result = runGradleTask(RUN_FREGE_TASK_NAME);
-                        assertTrue(project.getTasks().getByName(RUN_FREGE_TASK_NAME) instanceof RunFregeTask);
-                        assertEquals(SUCCESS, result.task(":" + RUN_FREGE_TASK_NAME).getOutcome());
-                        assertTrue(result.getOutput().contains("Frege rocks"));
-                }
-
-                @Test
-                void given_frege_file_without_main_function() throws Exception {
-                        String completionFr = "Completion.fr";
-                        String buildFileConfig = createFregeSection(
-                                        fregeBuilder.version("'3.25.84'").release("'3.25alpha'")
-                                                        .mainModule("'ch.fhnw.thga.Completion'").build());
-                        setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr, buildFileConfig);
-
-                        BuildResult result = runAndFailGradleTask(RUN_FREGE_TASK_NAME);
-                        assertTrue(project.getTasks().getByName(RUN_FREGE_TASK_NAME) instanceof RunFregeTask);
-                        assertEquals(FAILED, result.task(":" + RUN_FREGE_TASK_NAME).getOutcome());
-                        assertTrue(result.getOutput().contains("Main method not found"));
-                }
-
-                @Test
-                void given_frege_file_with_main_function_and_main_module_command_line_option() throws Exception {
-                        String fregeCode = String.join(NEW_LINE, "module ch.fhnw.thga.Main where", NEW_LINE, NEW_LINE,
-                                        "  main = do", NEW_LINE, "    println \"Frege rocks\"", NEW_LINE);
-                        String mainFr = "Main.fr";
-                        String buildFileConfig = createFregeSection(
-                                        fregeBuilder.version("'3.25.84'").release("'3.25alpha'").build());
-                        setupDefaultFregeProjectStructure(fregeCode, mainFr, buildFileConfig);
-
-                        BuildResult result = runGradleTask(RUN_FREGE_TASK_NAME, "--mainModule=ch.fhnw.thga.Main");
-                        assertTrue(project.getTasks().getByName(RUN_FREGE_TASK_NAME) instanceof RunFregeTask);
-                        assertEquals(SUCCESS, result.task(":" + RUN_FREGE_TASK_NAME).getOutcome());
-                        assertTrue(result.getOutput().contains("Frege rocks"));
-                }
-        }
-
-        @Nested
-        @TestInstance(Lifecycle.PER_CLASS)
-        @IndicativeSentencesGeneration(separator = " -> ", generator = DisplayNameGenerator.ReplaceUnderscores.class)
-        class Deps_frege_task_works {
-                @Test
-                void given_minimal_build_file_config() throws Exception {
-                        String completionFr = "Completion.fr";
-                        String minimalBuildFileConfig = createFregeSection(
-                                        fregeBuilder.version("'3.25.84'").release("'3.25alpha'").build());
-                        setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr, minimalBuildFileConfig);
-
-                        BuildResult result = runGradleTask(DEPS_FREGE_TASK_NAME, "-q");
-                        assertTrue(project.getTasks().getByName(DEPS_FREGE_TASK_NAME) instanceof DependencyFregeTask);
-                        assertEquals(SUCCESS, result.task(":" + DEPS_FREGE_TASK_NAME).getOutcome());
-                        assertTrue(result.getOutput().contains("frege3.25.84.jar"));
-                }
-
-                @Test
-                void given_build_file_config_with_dependencies() throws Exception {
-                        String minimalBuildFileConfig = createFregeSection(
-                                        fregeBuilder.version("'3.25.84'").release("'3.25alpha'").build());
-                        String completionFr = "Completion.fr";
-                        setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr, minimalBuildFileConfig);
-                        appendToFile(buildFile, String.join("\n", "repositories {", "mavenCentral()", "}"));
-                        appendToFile(buildFile, String.join("\n", "dependencies {",
-                                        "implementation group: 'org.json', name: 'json', version: '20211205'", "}"));
-
-                        BuildResult result = runGradleTask(DEPS_FREGE_TASK_NAME, "-q");
-                        assertTrue(project.getTasks().getByName(DEPS_FREGE_TASK_NAME) instanceof DependencyFregeTask);
-                        assertEquals(SUCCESS, result.task(":" + DEPS_FREGE_TASK_NAME).getOutcome());
-                        assertTrue(result.getOutput().contains("frege3.25.84.jar"));
-                        assertTrue(result.getOutput().contains("org.json"));
-                }
-        }
-
-        @Nested
-        @TestInstance(Lifecycle.PER_CLASS)
-        @IndicativeSentencesGeneration(separator = " -> ", generator = DisplayNameGenerator.ReplaceUnderscores.class)
-        class Repl_frege_task_works {
-                @Test
-                void given_minimal_build_file_config() throws Exception {
-                        String completionFr = "Completion.fr";
-                        String minimalBuildFileConfig = createFregeSection(
-                                        fregeBuilder.version("'3.25.84'").release("'3.25alpha'").build());
-                        setupDefaultFregeProjectStructure(SIMPLE_FREGE_CODE, completionFr, minimalBuildFileConfig);
-
-                        BuildResult result = runGradleTask(REPL_FREGE_TASK_NAME, "-q");
-                        assertTrue(project.getTasks().getByName(REPL_FREGE_TASK_NAME) instanceof ReplFregeTask);
-                        assertEquals(SUCCESS, result.task(":" + REPL_FREGE_TASK_NAME).getOutcome());
-                        assertTrue(result.getOutput().contains("java -cp"));
-                        assertTrue(result.getOutput().contains("frege3.25.84.jar"));
-                }
+    }
+
+    @Nested
+    @TestInstance(Lifecycle.PER_CLASS)
+    @IndicativeSentencesGeneration(
+        separator = " -> ",
+        generator = DisplayNameGenerator.ReplaceUnderscores.class)
+    class Repl_frege_task_fails
+    {
+        @Test
+        void given_minimal_build_file_config_without_repl_module() throws Exception
+        {
+            String completionFr           = "Completion.fr";
+            String minimalBuildFileConfig = createFregeSection(
+                fregeBuilder
+                .version("'3.25.84'")
+                .release("'3.25alpha'")
+                .build());
+            setupDefaultFregeProjectStructure(
+                SIMPLE_FREGE_CODE,
+                completionFr,
+                minimalBuildFileConfig);
+
+            BuildResult result = runAndFailGradleTask(REPL_FREGE_TASK_NAME);
+
+            assertTrue(
+                project.getTasks().getByName(REPL_FREGE_TASK_NAME)
+                instanceof ReplFregeTask);
+            assertEquals(FAILED, result.task(":" + COMPILE_FREGE_TASK_NAME).getOutcome());
         }
+    }
 }
\ No newline at end of file