Add unit tests for Listener and fix the test runtime

.github/workflows/run-ui-tests.yml

@@ -5,8 +5,7 @@
 # the old runIdeForUiTests setup there is no separate "start the IDE and wait for the robot server"
 # dance - the task is all that has to run.
 #
-# Note: there are no UI tests in the project yet, so the task currently runs an empty suite. The
-# workflow exists so that adding the first test under src/test is enough to get it covered here.
+# Tests are under src/test and require the JUnit 4 runtime dependency.
 #
 # Please check https://plugins.jetbrains.com/docs/intellij/testing-plugins.html for information
 # about testing plugins.

CHANGELOG.md

@@ -3,9 +3,19 @@
 # InlineProblems Changelog
 
 ## [Unreleased]
+
+### Added
+
+- Unit tests for the different problem detection strategies, making sure there are no duplicate IDs and that every ID maps back to its listener
+
 ### Changed
+
 - The GitHub release draft is created when a release is merged into the release branch, no longer on every push to main, so it cannot be published before the code is on the release branch
 
+### Fixed
+
+- JUnit 4 class could not be found when running tests due to a missing dependency in build.gradle.kts, JUnit 5 refers to JUnit 4 in IntelliJ
+
 ## [0.6.1] - 2026-10-13
 
 ### Fixed

build.gradle.kts

@@ -43,6 +43,9 @@ dependencies {
     testImplementation(platform("org.junit:junit-bom:${properties("junitVersion").get()}"))
     testImplementation("org.junit.jupiter:junit-jupiter")
     testRuntimeOnly("org.junit.platform:junit-platform-launcher")
+    // JUnit 5 Test Framework refers to JUnit 4 - see IntelliJ Platform Gradle Plugin FAQ
+    // https://plugins.jetbrains.com/docs/intellij/tools-intellij-platform-gradle-plugin-faq.html
+    testRuntimeOnly("junit:junit:4.13.2")
 }
 
 // Configure the IntelliJ Platform Gradle Plugin
@@ -148,8 +151,7 @@ qodana {
  * Replaces the runIdeForUiTests task of the old gradle-intellij-plugin, which drove the IDE
  * through the robot-server plugin - the 2.x plugin uses the IntelliJ Starter framework.
  *
- * There are no UI tests yet, so the task currently runs an empty suite. The plumbing is here so
- * that adding the first test under src/test/java is all it takes. */
+ * Tests are under src/test and require the JUnit 4 runtime dependency. */
 intellijPlatformTesting.testIdeUi.register("testIdeUi") {
     task {
         useJUnitPlatform()
@@ -164,8 +166,8 @@ tasks {
         useJUnitPlatform()
     }
 
-    // Pointless without test sources, and running both instrumentation tasks in one build
-    // crashes InstrumentCodeTask ("1 >= 1"). instrumentCode still covers the shipped code.
+    // Running both instrumentation tasks in one build crashes InstrumentCodeTask ("1 >= 1").
+    // instrumentCode still covers the shipped code.
     named("instrumentTestCode") {
         enabled = false
     }

src/test/java/org/overengineer/inlineproblems/entities/enums/ListenerTest.java

@@ -0,0 +1,44 @@
+package org.overengineer.inlineproblems.entities.enums;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+import java.util.*;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class ListenerTest {
+    @Test
+    void idsAreUnique() {
+        Set<Integer> knownIds = new HashSet<>();
+        List<Integer> duplicateIds = new ArrayList<>();
+
+        for (Listener listener : Listener.values()) {
+            if (!knownIds.add(listener.getId())) {
+                duplicateIds.add(listener.getId());
+            }
+        }
+
+        assertEquals(List.of(), duplicateIds);
+    }
+
+    @Test
+    void fromIdReturnsCorrectListener() {
+        List<Listener> mismatchedListeners = new ArrayList<>();
+
+        for (Listener listener : Listener.values()) {
+            if (listener != Listener.fromId(listener.getId())) {
+                mismatchedListeners.add(listener);
+            }
+        }
+
+        assertEquals(List.of(), mismatchedListeners);
+    }
+
+    @ParameterizedTest
+    @ValueSource(ints = {Integer.MIN_VALUE, -1, 99, Integer.MAX_VALUE})
+    void fromIdReturnsDefaultForUnknownId(int unknownId) {
+        assertEquals(Listener.DEFAULT, Listener.fromId(unknownId));
+    }
+}