Test arguments are skipped during title parameter injection

[krizalys]

🐛 Bug Report

In some cases, test arguments are skipped during title parameter injection.

To Reproduce

Consider the following Jest test:

class MyClass {
  constructor(value) {
    this.value = value
  }
}

describe("Test arguments are skipped during title parameter injection", () => {
  test.each([
    ["%d", new Object("My object")]
  ])("given \"%s\", returns %p", () => {
  })
})

Running it produces:

 PASS  test/unit/TestArgsSkipped.test.js
  Test arguments are skipped during title parameter injection
    ✓ given "NaN", returns %p

The title parameters have not been substituted as expected. The first one, %s, has been substituted by the (non-)number NaN, suggesting some confusion with the actual injected value of %d, and the second one, %p has not subtituted at all.

From what I observed, two conditions must be met at the same time for this to happen:

• Having test arguments looking like parameter placeholder themselves: %d in my example
• Having certain object arguments - does seem to happen with all prototypes, perhaps the presence of a toString function matters

Expected behavior

 PASS  test/unit/TestArgsSkipped.test.js
  Test arguments are skipped during title parameter injection
    ✓ given "%d", returns {"value": "My object"} (1ms)

Link to repl or repo (highly encouraged)

Cannot provide this, since test.each seems to have been introduced in Jest 23, whereas repl.it is currently using Jest 22.

Run npx envinfo --preset jest

Paste the results here:

npx: installed 1 in 0.737s

  System:
    OS: Linux 5.0 Arch Linux
    CPU: (8) x64 Intel(R) Core(TM) i7-7700 CPU @ 3.60GHz
  Binaries:
    Node: 11.13.0 - /usr/bin/node
    npm: 6.9.0 - /usr/bin/npm
  npmPackages:
    jest: ^24.7.1 => 24.7.1 

[SimenB]

/cc @mattphillips

[mattphillips]

@krizalys yup seems to be a bug nice catch! I've opened up a PR with a fix 😄

[github-actions]

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