fix: add @vitest/coverage-v8 dep and restructure test helper to assert outside try/catch

Signed-off-by: Jonathan Norris <jonathan.norris@dynatrace.com>

Author: jonathannorris

package-lock.json

@@ -45,6 +45,7 @@
     "@types/node": "^24.12.0",
     "@types/object-hash": "^3.0.6",
     "@types/semver": "^7.7.1",
+    "@vitest/coverage-v8": "^4.1.2",
     "eslint": "^10.1.0",
     "husky": "^9.1.7",
     "lint-staged": "^16.2.7",

package.json

@@ -5,18 +5,19 @@ type ErrorWithCause = Error & {
 export function expectInvalidConfigError(action: () => void, causePattern?: RegExp): void {
   const consoleDebugSpy = vi.spyOn(console, 'debug').mockImplementation(() => {});
 
+  let thrownError: ErrorWithCause | undefined;
   try {
     action();
-    throw new Error('Expected invalid flag configuration to throw');
   } catch (error) {
-    const invalidConfigError = error as ErrorWithCause;
-
-    expect(invalidConfigError.message).toBe('invalid flagd flag configuration');
-
-    if (causePattern) {
-      expect(invalidConfigError.cause?.message ?? '').toMatch(causePattern);
-    }
+    thrownError = error as ErrorWithCause;
   } finally {
     consoleDebugSpy.mockRestore();
   }
+
+  expect(thrownError).toBeDefined();
+  expect(thrownError!.message).toBe('invalid flagd flag configuration');
+
+  if (causePattern) {
+    expect(thrownError!.cause?.message ?? '').toMatch(causePattern);
+  }
 }