Throw error when duplicate snapshot name

e2e/__tests__/toMatchNamedSnapshot.test.ts

@@ -308,6 +308,28 @@ test('handles property matchers with deep properties', () => {
   }
 });
 
+test('error duplicate snapshot name', () => {
+  const filename = 'duplicate-match-named-snapshot.test.js';
+  const template = makeTemplate(
+    `test('duplicate named snapshots', () => {
+          expect($1).toMatchNamedSnapshot('basic-support');
+          expect($1).toMatchNamedSnapshot('basic-support');
+        });
+    `,
+  );
+  {
+    writeFiles(TESTS_DIR, {[filename]: template(['test'])});
+    const {stderr, exitCode} = runJest(DIR, ['-w=1', '--ci=false', filename]);
+    console.log(stderr);
+
+    expect(stderr).toMatch(
+      'The specific snapshot name was duplicate with the other snapshot.',
+    );
+    expect(stderr).toMatch('Snapshot name: basic-support');
+    expect(exitCode).toBe(1);
+  }
+});
+
 test('support concurrent testing', () => {
   const filename = 'match-snapshot-when-test-concurrent.test.js';
   const template = makeTemplate(`describe('group 1', () => {

packages/jest-snapshot/src/index.ts

@@ -36,7 +36,12 @@ import type {
   MatchSnapshotConfig,
   SnapshotNameConfig,
 } from './types';
-import {deepMerge, escapeBacktickString, serialize} from './utils';
+import {
+  deepMerge,
+  escapeBacktickString,
+  serialize,
+  testNameToKey,
+} from './utils';
 
 export {addSerializer, getSerializers} from './plugins';
 export {
@@ -439,7 +444,14 @@ const _toMatchSnapshot = (config: MatchSnapshotConfig) => {
     received,
     testName: fullTestName,
   });
-  const {actual, count, expected, pass} = result;
+  const {actual, count, expected, key, pass} = result;
+
+  if (snapshotName && key == testNameToKey(fullTestName, 1)) {
+    throw new Error(
+      'The specific snapshot name was duplicate with the other snapshot.\n\n' +
+        `Snapshot name: ${snapshotName}`,
+    );
+  }
 
   if (pass) {
     return {message: () => '', pass: true};