diff --git a/modules/core/src/main/java/org/approvej/approve/StackTraceTestFinderUtil.java b/modules/core/src/main/java/org/approvej/approve/StackTraceTestFinderUtil.java
index 8018603..6e1f0b4 100644
--- a/modules/core/src/main/java/org/approvej/approve/StackTraceTestFinderUtil.java
+++ b/modules/core/src/main/java/org/approvej/approve/StackTraceTestFinderUtil.java
@@ -6,6 +6,7 @@
 import java.lang.reflect.Method;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.List;
 import java.util.Optional;
 import java.util.stream.Stream;
 import org.jspecify.annotations.NullMarked;
@@ -67,7 +68,7 @@ public static Path findTestSourcePath(Method testMethod) {
             .replace("-classes", "");
     String packagePath = declaringClass.getPackageName().replace(".", "/");
     String pathRegex =
-        "(?!build|target).*%s.*/%s/%s\\.(java|kt|groovy|scala)$"
+        "(?!(?:build|target|bin|out)/).*%s.*/%s/%s\\.(java|kt|groovy|scala)$"
             .formatted(sourceSetName, packagePath, declaringClass.getSimpleName());
     try (Stream<Path> pathStream =
         Files.find(
@@ -75,10 +76,21 @@ public static Path findTestSourcePath(Method testMethod) {
             packageDepth + 10,
             (path, attributes) ->
                 attributes.isRegularFile() && path.normalize().toString().matches(pathRegex))) {
-      return pathStream
-          .findFirst()
-          .map(Path::normalize)
-          .orElseThrow(() -> new FileApproverError("Could not locate test source file"));
+      List<Path> matches = pathStream.map(Path::normalize).toList();
+      return switch (matches.size()) {
+        case 0 -> throw new FileApproverError("Could not locate test source file");
+        case 1 -> matches.getFirst();
+        default -> {
+          List<Path> srcMatches =
+              matches.stream().filter(path -> path.toString().contains("src")).toList();
+          if (srcMatches.size() == 1) {
+            yield srcMatches.getFirst();
+          }
+          throw new FileApproverError(
+              "Found multiple test source files (%d contain 'src'): %s"
+                  .formatted(srcMatches.size(), matches));
+        }
+      };
     } catch (IOException e) {
       throw new FileApproverError("Could not traverse code directory", e);
     }
diff --git a/modules/core/src/test/java/org/approvej/approve/StackTraceTestFinderUtilTest.java b/modules/core/src/test/java/org/approvej/approve/StackTraceTestFinderUtilTest.java
index 1e9dd5e..d14bd0f 100644
--- a/modules/core/src/test/java/org/approvej/approve/StackTraceTestFinderUtilTest.java
+++ b/modules/core/src/test/java/org/approvej/approve/StackTraceTestFinderUtilTest.java
@@ -3,6 +3,7 @@
 import static java.nio.file.Files.copy;
 import static java.nio.file.Files.createDirectories;
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 import java.io.IOException;
 import java.lang.reflect.Method;
@@ -61,11 +62,17 @@ void findTestSourcePath() {
     assertThat(testSourcePath).isEqualTo(thisTestSourcePath.normalize());
   }
 
-  @Test
-  void findTestSourcePath_file_in_build() throws IOException {
-    Path wrongTestSourcePath =
-        Path.of(
-            "build/spotless-clean/spotlessJava/java/test/org/approvej/approve/StackTraceTestFinderUtilTest.java");
+  @ParameterizedTest
+  @ValueSource(
+      strings = {
+        "build/spotless-clean/spotlessJava/java/test/org/approvej/approve/StackTraceTestFinderUtilTest.java",
+        "target/spotless-clean/spotlessJava/java/test/org/approvej/approve/StackTraceTestFinderUtilTest.java",
+        "bin/test/org/approvej/approve/StackTraceTestFinderUtilTest.java",
+        "out/test/org/approvej/approve/StackTraceTestFinderUtilTest.java",
+        "other/test/java/org/approvej/approve/StackTraceTestFinderUtilTest.java",
+      })
+  void findTestSourcePath_duplicate_file(String wrongPath) throws IOException {
+    Path wrongTestSourcePath = Path.of(wrongPath);
     wrongTestSourcePathsToCleanup.add(wrongTestSourcePath);
     createDirectories(wrongTestSourcePath.getParent());
     copy(thisTestSourcePath, wrongTestSourcePath);
@@ -78,18 +85,27 @@ void findTestSourcePath_file_in_build() throws IOException {
   }
 
   @Test
-  void findTestSourcePath_file_in_target() throws IOException {
+  void findTestSourcePath_no_source_file() throws NoSuchMethodException {
+    Method method =
+        org.assertj.core.api.Assertions.class.getDeclaredMethod("assertThat", boolean.class);
+
+    assertThatThrownBy(() -> StackTraceTestFinderUtil.findTestSourcePath(method))
+        .isInstanceOf(FileApproverError.class)
+        .hasMessage("Could not locate test source file");
+  }
+
+  @Test
+  void findTestSourcePath_ambiguous() throws IOException {
     Path wrongTestSourcePath =
-        Path.of(
-            "target/spotless-clean/spotlessJava/java/test/org/approvej/approve/StackTraceTestFinderUtilTest.java");
+        Path.of("other/src/test/java/org/approvej/approve/StackTraceTestFinderUtilTest.java");
     wrongTestSourcePathsToCleanup.add(wrongTestSourcePath);
     createDirectories(wrongTestSourcePath.getParent());
     copy(thisTestSourcePath, wrongTestSourcePath);
 
-    Path testSourcePath =
-        StackTraceTestFinderUtil.findTestSourcePath(
-            StackTraceTestFinderUtil.currentTestMethod().method());
+    Method method = StackTraceTestFinderUtil.currentTestMethod().method();
 
-    assertThat(testSourcePath).isEqualTo(thisTestSourcePath.normalize());
+    assertThatThrownBy(() -> StackTraceTestFinderUtil.findTestSourcePath(method))
+        .isInstanceOf(FileApproverError.class)
+        .hasMessageStartingWith("Found multiple test source files (");
   }
 }