jest-each

---

A parameterised testing library for Jest inspired by mocha-each.

jest-each allows you to provide multiple arguments to your test/describe which results in the test/suite being run once per row of parameters.

Features

• .test to runs multiple tests with parameterised data
  • Also under the alias: .it
• .test.only to only run the parameterised tests
  • Also under the aliases: .it.only or .fit
• .test.skip to skip the parameterised tests
  • Also under the aliases: .it.skip or .xit or .xtest
• .describe to runs test suites with parameterised data
• .describe.only to only run the parameterised suite of tests
  • Also under the aliases: .fdescribe
• .describe.skip to skip the parameterised suite of tests
  • Also under the aliases: .xdescribe
• Asynchronous tests with done
• Unique test titles with printf formatting:
  • %p - pretty-format.
  • %s- String.
  • %d- Number.
  • %i - Integer.
  • %f - Floating point value.
  • %j - JSON.
  • %o - Object.
  • %# - Index of the test case.
  • %% - single percent sign ('%'). This does not consume an argument.
• 🖖 Spock like data tables with Tagged Template Literals

---

• Demo
• Installation
• Importing
• APIs
  • Array of Rows
    • Usage
  • Tagged Template Literal of rows
    • Usage

Demo

Tests without jest-each

Tests can be re-written with jest-each to:

.test

.test with Tagged Template Literals

.describe

Installation

npm i --save-dev jest-each

yarn add -D jest-each

Importing

jest-each is a default export so it can be imported with whatever name you like.

// es6
import each from 'jest-each';

// es5
const each = require('jest-each').default;

Array of rows

API

each([parameters]).test(name, testFn)

each:

• parameters: Array of Arrays with the arguments that are passed into the testFn for each row
  • Note If you pass in a 1D array of primitives, internally it will be mapped to a table i.e. [1, 2, 3] -> [[1], [2], [3]]

.test:

• name: String the title of the test.
  • Generate unique test titles by positionally injecting parameters with printf formatting:
    • %p - pretty-format.
    • %s- String.
    • %d- Number.
    • %i - Integer.
    • %f - Floating point value.
    • %j - JSON.
    • %o - Object.
    • %# - Index of the test case.
    • %% - single percent sign ('%'). This does not consume an argument.
• testFn: Function the test logic, this is the function that will receive the parameters of each row as function arguments

each([parameters]).describe(name, suiteFn)

each:

• parameters: Array of Arrays with the arguments that are passed into the suiteFn for each row
  • Note If you pass in a 1D array of primitives, internally it will be mapped to a table i.e. [1, 2, 3] -> [[1], [2], [3]]

.describe:

• name: String the title of the describe
  • Generate unique test titles by positionally injecting parameters with printf formatting:
    • %p - pretty-format.
    • %s- String.
    • %d- Number.
    • %i - Integer.
    • %f - Floating point value.
    • %j - JSON.
    • %o - Object.
    • %# - Index of the test case.
    • %% - single percent sign ('%'). This does not consume an argument.
• suiteFn: Function the suite of test/its to be ran, this is the function that will receive the parameters in each row as function arguments

Usage

.test(name, fn)

Alias: .it(name, fn)

each([[1, 1, 2], [1, 2, 3], [2, 1, 3]]).test(
  'returns the result of adding %d to %d',
  (a, b, expected) => {
    expect(a + b).toBe(expected);
  },
);

.test.only(name, fn)

Aliases: .it.only(name, fn) or .fit(name, fn)

each([[1, 1, 2], [1, 2, 3], [2, 1, 3]]).test.only(
  'returns the result of adding %d to %d',
  (a, b, expected) => {
    expect(a + b).toBe(expected);
  },
);

.test.skip(name, fn)

Aliases: .it.skip(name, fn) or .xit(name, fn) or .xtest(name, fn)

each([[1, 1, 2], [1, 2, 3], [2, 1, 3]]).test.skip(
  'returns the result of adding %d to %d',
  (a, b, expected) => {
    expect(a + b).toBe(expected);
  },
);

Asynchronous .test(name, fn(done))

Alias: .it(name, fn(done))

each([['hello'], ['mr'], ['spy']]).test(
  'gives 007 secret message: %s',
  (str, done) => {
    const asynchronousSpy = message => {
      expect(message).toBe(str);
      done();
    };
    callSomeAsynchronousFunction(asynchronousSpy)(str);
  },
);

.describe(name, fn)

each([[1, 1, 2], [1, 2, 3], [2, 1, 3]]).describe(
  '.add(%d, %d)',
  (a, b, expected) => {
    test(`returns ${expected}`, () => {
      expect(a + b).toBe(expected);
    });

    test('does not mutate first arg', () => {
      a + b;
      expect(a).toBe(a);
    });

    test('does not mutate second arg', () => {
      a + b;
      expect(b).toBe(b);
    });
  },
);

.describe.only(name, fn)

Aliases: .fdescribe(name, fn)

each([[1, 1, 2], [1, 2, 3], [2, 1, 3]]).describe.only(
  '.add(%d, %d)',
  (a, b, expected) => {
    test(`returns ${expected}`, () => {
      expect(a + b).toBe(expected);
    });
  },
);

.describe.skip(name, fn)

Aliases: .xdescribe(name, fn)

each([[1, 1, 2], [1, 2, 3], [2, 1, 3]]).describe.skip(
  '.add(%d, %d)',
  (a, b, expected) => {
    test(`returns ${expected}`, () => {
      expect(a + b).toBe(expected);
    });
  },
);

---

Tagged Template Literal of rows

API

each[tagged template].test(name, suiteFn)

each`
  a    | b    | expected
  ${1} | ${1} | ${2}
  ${1} | ${2} | ${3}
  ${2} | ${1} | ${3}
`.test('returns $expected when adding $a to $b', ({a, b, expected}) => {
  expect(a + b).toBe(expected);
});

each takes a tagged template string with:

• First row of variable name column headings seperated with |
• One or more subsequent rows of data supplied as template literal expressions using ${value} syntax.

.test:

• name: String the title of the test, use $variable in the name string to inject test values into the test title from the tagged template expressions
  • To inject nested object values use you can supply a keyPath i.e. $variable.path.to.value
• testFn: Function the test logic, this is the function that will receive the parameters of each row as function arguments

each[tagged template].describe(name, suiteFn)

each`
  a    | b    | expected
  ${1} | ${1} | ${2}
  ${1} | ${2} | ${3}
  ${2} | ${1} | ${3}
`.describe('$a + $b', ({a, b, expected}) => {
  test(`returns ${expected}`, () => {
    expect(a + b).toBe(expected);
  });

  test('does not mutate first arg', () => {
    a + b;
    expect(a).toBe(a);
  });

  test('does not mutate second arg', () => {
    a + b;
    expect(b).toBe(b);
  });
});

each takes a tagged template string with:

• First row of variable name column headings seperated with |
• One or more subsequent rows of data supplied as template literal expressions using ${value} syntax.

.describe:

• name: String the title of the test, use $variable in the name string to inject test values into the test title from the tagged template expressions
  • To inject nested object values use you can supply a keyPath i.e. $variable.path.to.value
• suiteFn: Function the suite of test/its to be ran, this is the function that will receive the parameters in each row as function arguments

Usage

.test(name, fn)

Alias: .it(name, fn)

each`
  a    | b    | expected
  ${1} | ${1} | ${2}
  ${1} | ${2} | ${3}
  ${2} | ${1} | ${3}
`.test('returns $expected when adding $a to $b', ({a, b, expected}) => {
  expect(a + b).toBe(expected);
});

.test.only(name, fn)

Aliases: .it.only(name, fn) or .fit(name, fn)

each`
  a    | b    | expected
  ${1} | ${1} | ${2}
  ${1} | ${2} | ${3}
  ${2} | ${1} | ${3}
`.test.only('returns $expected when adding $a to $b', ({a, b, expected}) => {
  expect(a + b).toBe(expected);
});

.test.skip(name, fn)

Aliases: .it.skip(name, fn) or .xit(name, fn) or .xtest(name, fn)

each`
  a    | b    | expected
  ${1} | ${1} | ${2}
  ${1} | ${2} | ${3}
  ${2} | ${1} | ${3}
`.test.skip('returns $expected when adding $a to $b', ({a, b, expected}) => {
  expect(a + b).toBe(expected);
});

Asynchronous .test(name, fn(done))

Alias: .it(name, fn(done))

each`
  str
  ${'hello'}
  ${'mr'}
  ${'spy'}
`.test('gives 007 secret message: $str', ({str}, done) => {
  const asynchronousSpy = message => {
    expect(message).toBe(str);
    done();
  };
  callSomeAsynchronousFunction(asynchronousSpy)(str);
});

.describe(name, fn)

each`
  a    | b    | expected
  ${1} | ${1} | ${2}
  ${1} | ${2} | ${3}
  ${2} | ${1} | ${3}
`.describe('$a + $b', ({a, b, expected}) => {
  test(`returns ${expected}`, () => {
    expect(a + b).toBe(expected);
  });

  test('does not mutate first arg', () => {
    a + b;
    expect(a).toBe(a);
  });

  test('does not mutate second arg', () => {
    a + b;
    expect(b).toBe(b);
  });
});

.describe.only(name, fn)

Aliases: .fdescribe(name, fn)

each`
  a    | b    | expected
  ${1} | ${1} | ${2}
  ${1} | ${2} | ${3}
  ${2} | ${1} | ${3}
`.describe.only('$a + $b', ({a, b, expected}) => {
  test(`returns ${expected}`, () => {
    expect(a + b).toBe(expected);
  });
});

.describe.skip(name, fn)

Aliases: .xdescribe(name, fn)

each`
  a    | b    | expected
  ${1} | ${1} | ${2}
  ${1} | ${2} | ${3}
  ${2} | ${1} | ${3}
`.describe.skip('$a + $b', ({a, b, expected}) => {
  test(`returns ${expected}`, () => {
    expect(a + b).toBe(expected);
  });
});

License

MIT