test(breadcrumbs): assert strict null on non-exact route map lookups

tests/phase22/breadcrumb-route-maps-helper.test.cjs

@@ -215,6 +215,56 @@ test("resolveMappedRouteRenderer returns null for unmapped path", () => {
     );
 });
 
+test("resolveMappedRouteRenderer returns null for empty, whitespace, and non-exact path variants", () => {
+    const { buildBreadcrumbRendererMaps, resolveMappedRouteRenderer } =
+        loadHelpers();
+
+    const knownRenderer = () => "known";
+
+    const maps = buildBreadcrumbRendererMaps({
+        simpleRouteRenderersByPath: {
+            "/known": knownRenderer
+        },
+        simpleLinkTextPairRenderersByPath: {},
+        simpleMyPortalRouteRenderersByPath: {},
+        newAppealRouteRenderersByPath: {},
+        callbackRouteRenderersByPath: {},
+        stepBackRouteRenderersByPath: {},
+        caseDetailRouteRenderersByPath: {},
+        detailAndAccountRouteRenderersByPath: {}
+    });
+
+    assert.strictEqual(
+        resolveMappedRouteRenderer("", maps),
+        null,
+        "Expected null for empty path lookup when no empty key is mapped"
+    );
+
+    assert.strictEqual(
+        resolveMappedRouteRenderer("   ", maps),
+        null,
+        "Expected null for whitespace-only path lookup"
+    );
+
+    assert.strictEqual(
+        resolveMappedRouteRenderer("/known ", maps),
+        null,
+        "Expected null for non-exact path variant with trailing whitespace"
+    );
+
+    assert.strictEqual(
+        resolveMappedRouteRenderer(" /known", maps),
+        null,
+        "Expected null for non-exact path variant with leading whitespace"
+    );
+
+    assert.strictEqual(
+        resolveMappedRouteRenderer("/KNOWN", maps),
+        null,
+        "Expected null for non-exact case-variant path lookup"
+    );
+});
+
 test("resolveMappedRouteRenderer skips invalid map entries and non-function renderer values", () => {
     const { buildBreadcrumbRendererMaps, resolveMappedRouteRenderer } =
         loadHelpers();