test(submodule): cover remaining Sonar branches

Add focused tests for branch suffix parsing and workspace validation fallback handling so the submodule coverage report no longer has uncovered lines or branches in src/core/submodule.ts.

Local verification:

- npm run lint --workspace git-id-switcher -- --no-cache

- npm run compile --workspace git-id-switcher

- npm run test:coverage --workspace git-id-switcher

Signed-off-by: Null;Variant <null@nullvariant.com>

🖥️ IDE: [Zed](https://zed.dev/)

Co-authored-by: GPT-5.5 <codex@openai.com>
Model-Raw: gpt-5.5

Author: nullvariant

extensions/git-id-switcher/src/core/submodule.ts

@@ -122,6 +122,12 @@ function stripBranchSuffix(str: string): string {
 }
 /* c8 ignore stop */
 
+function getWorkspaceValidationFailureReason(workspaceValidation: {
+  reason?: string;
+}): string {
+  return workspaceValidation.reason ?? "Invalid workspace path";
+}
+
 /**
  * Parse and validate a single submodule entry from git status output.
  * Uses pure string operations to prevent ReDoS vulnerabilities.
@@ -270,7 +276,7 @@ export async function listSubmodules(
   if (!workspaceValidation.valid || !workspaceValidation.normalizedPath) {
     securityLogger.logValidationFailure(
       "submoduleWorkspace",
-      workspaceValidation.reason ?? "Invalid workspace path",
+      getWorkspaceValidationFailureReason(workspaceValidation),
     );
     return [];
   }
@@ -534,5 +540,7 @@ export function getMaxSubmoduleDepth(): number {
  * Test-only exports for private validation helpers.
  */
 export const __testExports = {
+  getWorkspaceValidationFailureReason,
   isValidCommitHash,
+  stripBranchSuffix,
 };

extensions/git-id-switcher/src/test/submodule.test.ts

@@ -430,6 +430,55 @@ function testCommitHashValidation(): void {
   console.log('  Commit hash validation tests passed');
 }
 
+/**
+ * Test branch suffix parsing branch coverage.
+ */
+function testBranchSuffixParsing(): void {
+  console.log('Testing branch suffix parsing...');
+
+  const { stripBranchSuffix } = __testExports;
+
+  assert.strictEqual(
+    stripBranchSuffix('vendor/lib'),
+    'vendor/lib',
+    'Path without branch suffix should remain unchanged'
+  );
+  assert.strictEqual(
+    stripBranchSuffix('vendor/lib main)'),
+    'vendor/lib main)',
+    'Malformed suffix without opening parenthesis should remain unchanged'
+  );
+  assert.strictEqual(
+    stripBranchSuffix('vendor/lib (main)'),
+    'vendor/lib',
+    'Valid branch suffix should be stripped'
+  );
+
+  console.log('  Branch suffix parsing tests passed');
+}
+
+/**
+ * Test workspace validation failure reason fallback branch coverage.
+ */
+function testWorkspaceValidationFailureReason(): void {
+  console.log('Testing workspace validation failure reason...');
+
+  const { getWorkspaceValidationFailureReason } = __testExports;
+
+  assert.strictEqual(
+    getWorkspaceValidationFailureReason({ reason: 'Workspace path is empty' }),
+    'Workspace path is empty',
+    'Provided workspace validation reason should be used'
+  );
+  assert.strictEqual(
+    getWorkspaceValidationFailureReason({}),
+    'Invalid workspace path',
+    'Fallback reason should be used when validation has no reason'
+  );
+
+  console.log('  Workspace validation failure reason tests passed');
+}
+
 /**
  * Test regex pattern strictness (40-char SHA-1)
  *
@@ -1168,6 +1217,8 @@ export async function runSubmoduleTests(): Promise<void> {
     testMaxSubmoduleDepth();
     testWorkspaceBoundary();
     testCommitHashValidation();
+    testBranchSuffixParsing();
+    testWorkspaceValidationFailureReason();
     testRegexPatternStrictness();
     testInvalidWorkspacePaths();