Proposal: include snapshot name in error message

[hroemer]

Current behavior

with a jest configuration like this:

module.exports = {
    transform: {
        "^.+\\.tsx?$": "ts-jest"
    },
    testRegex: "(./specs/.*/.*(\\.test|\\.spec))\\.(ts?|tsx?)$",
    moduleFileExtensions: [
        "ts",
        "js",
        "json",
    ]
};

Named snapshot test

Consider a snapshot based test including snapshot names for differentiation, e.g.:

test("Test1", () => {
    expect("VALUE1").toMatchSnapshot();
    expect("VALUE2").toMatchSnapshot("name");
    expect("VALUE3").toMatchSnapshot("another");
});

It will produce a snapshot file including the snapshot names (name, another) as well:

// Jest Snapshot v1, https://goo.gl/fbAQLP

exports[`Test1 1`] = `"VALUE1"`;

exports[`Test1: another 1`] = `"VALUE3"`;

exports[`Test1: name 1`] = `"VALUE2"`;

If in a subsequent run the test fails due to a failed expectation it will render this:

✕ Test1 (10ms)

  ● Test1

    expect(value).toMatchSnapshot()
    
    Received value does not match stored snapshot 1.
    
    - "VALUE3"
    + "VALUEX"

      2 |     expect("VALUE1").toMatchSnapshot();
      3 |     expect("VALUE2").toMatchSnapshot("name");
    > 4 |     expect("VALUEX").toMatchSnapshot("another");
      5 | });
      6 | 
      
      at Object.<anonymous>.test (specs/lib/jest/snap.spec.ts:4:22)

 › 1 snapshot test failed.

The failing snapshot line number is marked accordingly.

Wrapped expect hides origin

If the snapshot expect code is wrapped in some library function:

function testWrap(actual: string, snapshotName: string){
    expect(actual).toMatchSnapshot(snapshotName);
}

test("Test2", () => {
    testWrap("VALUE1", null);
    testWrap("VALUE2", "name");
    testWrap("VALUE3", "another");
});

and the test fails due to a failed expectation it will render this:

✕ Test2 (4ms)

  ● Test2

    expect(value).toMatchSnapshot()
    
    Received value does not match stored snapshot 1.
    
    - "VALUE2"
    + "VALUEX"

       6 | 
       7 | function testWrap(actual: string, snapshotName: string){
    >  8 |     expect(actual).toMatchSnapshot(snapshotName);
       9 | }
      10 | 
      11 | test("Test2", () => {
      
      at testWrap (specs/lib/jest/snap.spec.ts:8:20)
      at Object.<anonymous>.test (specs/lib/jest/snap.spec.ts:13:5)

 › 1 snapshot test failed.

Based on the originating line it is now hard to figure out which "sub" snapshot actually failed.

Proposal

Could you please add the snapshot name to the first error message? I.e. like this:

● Test2

    expect(value).toMatchSnapshot()
    
    Received value does not match stored snapshot "name" 1 .
    
    - "VALUE2"
    + "VALUEX"

[SimenB]

I think that's a great idea. It's a breaking change, but we're gearing up for version 23 anyways, so that's OK. Wanna send a PR for it?

[hroemer]

I just added a PR #6015 for it.

[github-actions]

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