add test for invalid preset json

packages/jest-config/src/__tests__/__snapshots__/normalize.test.js.snap

@@ -17,6 +17,17 @@ exports[`Upgrade help logs a warning when \`scriptPreprocessor\` and/or \`prepro
 <yellow></>"
 `;
 
+exports[`preset throws when preset is invalid 1`] = `
+"<red><bold><bold>● <bold>Validation Error</>:</>
+<red></>
+<red>  Preset <bold>react-native</> is invalid:</>
+<red>  Unexpected token } in JSON at position 104</>
+<red></>
+<red>  <bold>Configuration Documentation:</></>
+<red>  https://facebook.github.io/jest/docs/configuration.html</>
+<red></>"
+`;
+
 exports[`preset throws when preset not found 1`] = `
 "<red><bold><bold>● <bold>Validation Error</>:</>
 <red></>

packages/jest-config/src/__tests__/jest-preset.json

@@ -0,0 +1,7 @@
+{
+  "moduleNameMapper": {
+    "b": "b"
+  },
+  "modulePathIgnorePatterns": ["b"],
+  "setupFiles": ["b"],
+}

packages/jest-config/src/__tests__/normalize.test.js

@@ -877,6 +877,22 @@ describe('preset', () => {
     }).toThrowErrorMatchingSnapshot();
   });
 
+  test('throws when preset is invalid', () => {
+    jest.mock('/node_modules/react-native/jest-preset.json', () =>
+      require.requireActual('./jest-preset.json'),
+    );
+
+    expect(() => {
+      normalize(
+        {
+          preset: 'react-native',
+          rootDir: '/root/path/foo',
+        },
+        {},
+      );
+    }).toThrowErrorMatchingSnapshot();
+  });
+
   test('works with "react-native"', () => {
     expect(() => {
       normalize(