test: improve coverage for TestMethodDiviner classes

**What:**
Added unit tests covering the `index == -1` (no match) edge cases in `TestMethodDivinerNoPraefixTest` and `TestMethodDivinerJunit3PraefixTest`.

**Why:**
The previous refactoring from `replaceFirst` to `indexOf` introduced a new `if (index != -1)` branch which was not covered by existing tests, causing the Codecov CI check to fail due to a drop in diff coverage.

**Impact:**
Increases code coverage and ensures that renaming methods correctly fallback when the expected prefix/suffix string does not exist in the target string.

Co-authored-by: RoiSoleil <3462260+RoiSoleil@users.noreply.github.com>

Author: google-labs-jules[bot]

.jules/bolt.md

@@ -30,3 +30,6 @@
 ## 2026-05-22 - Replacing literal `replaceFirst` with manual string searches
 **Learning:** Using regex-based `replaceFirst` for literal search-and-replace, especially when dealing with prefixes or static replacements, is computationally expensive due to the overhead of `Pattern` compilation and matching. It is also prone to regex compilation bugs if the replacement target has regex reserved characters (like `$`). Swapping `replaceFirst` for a combination of `startsWith`, `indexOf`, and `substring` concatenation provides a significant performance boost in frequently called logic (like AST parsing inside `FilterMethodVisitor`).
 **Action:** When finding exact substring replacements or prefix removal, manually calculate indices and substring lengths using `indexOf`/`substring` instead of `replaceFirst`.
+## 2026-05-22 - Code Coverage Failures after refactoring regex
+**Learning:** When refactoring regex paths (like `replaceFirst`) into equivalent literal matches (`startsWith`, `indexOf`, `substring`), new specific edge-case branches (like `if (index != -1)`) might not have existing unit test coverage. This will trigger Codecov PR failures because the overall diff coverage drops below the required threshold.
+**Action:** When making logical refactorings, proactively add unit tests for the new conditional branches introduced by the refactoring, even if they seem trivial, to ensure CI coverage checks pass.

org.moreunit.test/test/org/moreunit/util/TestMethodDivinerJunit3PraefixTest.java

@@ -56,4 +56,11 @@ public void getTestMethodNameAfterRename()
         assertThat(testMethodDiviner.getTestMethodNameAfterRename("countMembers", "countAllMembers", "testCountMembersSpecialCase")).isEqualTo("testCountAllMembersSpecialCase");
         assertThat(testMethodDiviner.getTestMethodNameAfterRename("countMembers", "countAllMembers", "testCountMembers")).isEqualTo("testCountAllMembers");
     }
+
+    @Test
+    public void getTestMethodNameAfterRename_noMatch()
+    {
+        TestMethodDiviner testMethodDiviner = new TestMethodDivinerJunit3Praefix();
+        assertThat(testMethodDiviner.getTestMethodNameAfterRename("countMembers", "countAllMembers", "testSomethingElse")).isEqualTo("testSomethingElse");
+    }
 }

org.moreunit.test/test/org/moreunit/util/TestMethodDivinerNoPraefixTest.java

@@ -21,6 +21,13 @@ public void testGetTestMethodNameAfterRename() throws Exception
         assertThat(testMethodDivinerNoPraefix.getTestMethodNameAfterRename("getFoo", "get2Foo", "getFoo_getterWorks")).isEqualTo("get2Foo_getterWorks");
     }
 
+    @Test
+    public void testGetTestMethodNameAfterRename_noMatch() throws Exception
+    {
+        TestMethodDivinerNoPraefix testMethodDivinerNoPraefix = new TestMethodDivinerNoPraefix();
+        assertThat(testMethodDivinerNoPraefix.getTestMethodNameAfterRename("getFoo", "get2Foo", "somethingElse")).isEqualTo("somethingElse");
+    }
+
     @Test
     public void getMethodNameFromTestMethodName() throws Exception
     {

test_diviner.sh

@@ -0,0 +1 @@
+# check line numbers for missing coverage