Matching

Matching makes your tests more expressive and your tests less brittle.

Rather than use hard-coded values which must then be present on the Provider side, you can use regular expressions and type matches on objects and arrays to validate the structure of your APIs.

The matching rules you can use depend on the specification of the Pact file you need to generate

Matching Packages

Matching rules

V2 Matching rules

V2 only matching rules are found in the export Matchers of the @pact-foundation/pact package, and can be used with the PactV2 dsl.

Match common formats

Often times, you find yourself having to re-write regular expressions for common formats. We've created a number of them for you to save you the time:

Matchers API

method	description
`boolean`	Match a boolean value (using equality)
`string`	Match a string value
`integer`	Will match all numbers that are integers (both ints and longs)
`decimal`	Will match all real numbers (floating point and decimal)
`hexadecimal`	Will match all hexadecimal encoded strings
`iso8601Date`	Will match string containing basic ISO8601 dates (e.g. 2016-01-01)
`iso8601DateTime`	Will match string containing ISO 8601 formatted dates (e.g. 2015-08-06T16:53:10+01:00)
`iso8601DateTimeWithMillis`	Will match string containing ISO 8601 formatted dates, enforcing millisecond precision (e.g. 2015-08-06T16:53:10.123+01:00)
`rfc3339Timestamp`	Will match a string containing an RFC3339 formatted timestapm (e.g. Mon, 31 Oct 2016 15:21:41 -0400)
`iso8601Time`	Will match string containing times (e.g. T22:44:30.652Z)
`ipv4Address`	Will match string containing IP4 formatted address
`ipv6Address`	Will match string containing IP6 formatted address
`uuid`	Will match strings containing UUIDs
`email`	Will match strings containing Email address

Match based on type

const { like, string } = Matchers

provider.addInteraction({
  state: "Has some animals",
  uponReceiving: "a request for an animal",
  withRequest: {
    method: "GET",
    path: "/animals/1",
  },
  willRespondWith: {
    status: 200,
    headers: {
      "Content-Type": "application/json; charset=utf-8",
    },
    body: {
      id: 1,
      name: string("Billy"),
      address: like({
        street: "123 Smith St",
        suburb: "Smithsville",
        postcode: 7777,
      }),
    },
  },
})

Note that you can wrap a like around a single value or an object. When wrapped around an object, all values and child object values will be matched according to types, unless overridden by something more specific like a term.

Match based on arrays

Matching provides the ability to specify flexible length arrays. For example:

pact.eachLike(obj, { min: 3 })

Where obj can be any javascript object, value or Pact.Match. It takes optional argument ({ min: 3 }) where min is greater than 0 and defaults to 1 if not provided.

Below is an example that uses all of the Pact Matchers.

const { somethingLike: like, term, eachLike } = pact

const animalBodyExpectation = {
  id: 1,
  first_name: "Billy",
  last_name: "Goat",
  animal: "goat",
  age: 21,
  gender: term({
    matcher: "F|M",
    generate: "M",
  }),
  location: {
    description: "Melbourne Zoo",
    country: "Australia",
    post_code: 3000,
  },
  eligibility: {
    available: true,
    previously_married: false,
  },
  children: eachLike({ name: "Sally", age: 2 }),
}

// Define animal list payload, reusing existing object matcher
// Note that using eachLike ensure that all values are matched by type
const animalListExpectation = eachLike(animalBodyExpectation, {
  min: MIN_ANIMALS,
})

provider.addInteraction({
  state: "Has some animals",
  uponReceiving: "a request for all animals",
  withRequest: {
    method: "GET",
    path: "/animals/available",
  },
  willRespondWith: {
    status: 200,
    headers: {
      "Content-Type": "application/json; charset=utf-8",
    },
    body: animalListExpectation,
  },
})

Match by regular expression

If none of the above matchers or formats work, you can write your own regex matcher.

The underlying mock service is written in Ruby, so the regular expression must be in a Ruby format, not a Javascript format.

const { term } = pact

provider.addInteraction({
  state: "Has some animals",
  uponReceiving: "a request for an animal",
  withRequest: {
    method: "GET",
    path: "/animals/1",
  },
  willRespondWith: {
    status: 200,
    headers: {
      "Content-Type": "application/json; charset=utf-8",
    },
    body: {
      id: 100,
      name: "billy",
      gender: term({
        matcher: "F|M",
        generate: "F",
      }),
    },
  },
})

V3 Matching rules

V3 only matching rules are found in the export MatchersV3 of the @pact-foundation/pact package, and can be used with PactV3 DSL.

For example:

const { PactV3, MatchersV3 } = require("@pact-foundation/pact")
const {
  eachLike,
  atLeastLike,
  integer,
  timestamp,
  boolean,
  string,
  regex,
  like,
} = MatchersV3

const animalBodyExpectation = {
  id: integer(1),
  available_from: timestamp("yyyy-MM-dd'T'HH:mm:ss.SSSX"),
  first_name: string("Billy"),
  last_name: string("Goat"),
  animal: string("goat"),
  age: integer(21),
  gender: regex("F|M", "M"),
  location: {
    description: string("Melbourne Zoo"),
    country: string("Australia"),
    post_code: integer(3000),
  },
  eligibility: {
    available: boolean(true),
    previously_married: boolean(false),
  },
  interests: eachLike("walks in the garden/meadow"),
}

Matcher	Parameters	Description
`like`	template	Applies the `type` matcher to value, which requires values to have the same type as the template
`eachLike`	template	Applies the `type` matcher to each value in an array, ensuring they match the template. Note that this matcher does not validate the length of the array, and the items within it
`atLeastOneLike`	template, count: number = 1	Behaves like the `eachLike` matcher, but also applies a minimum length validation of one on the length of the array. The optional `count` parameter controls the number of examples generated.
`atLeastLike`	template, min: number, count?: number	Just like `atLeastOneLike`, but the minimum length is configurable.
`atMostLike`	template, max: number, count?: number	Behaves like the `eachLike` matcher, but also applies a maximum length validation on the length of the array. The optional `count` parameter controls the number of examples generated.
`constrainedArrayLike`	template, min: number, max: number, count?: number	Behaves like the `eachLike` matcher, but also applies a minimum and maximum length validation on the length of the array. The optional `count` parameter controls the number of examples generated.
`boolean`	example: boolean	Matches boolean values (true, false)
`integer`	example?: number	Value that must be an integer (must be a number and have no decimal places). If the example value is omitted, a V3 Random number generator will be used.
`decimal`	example?: number	Value that must be a decimal number (must be a number and have at least one digit in the decimal places). If the example value is omitted, a V3 Random number generator will be used.
`number`	example?: number	Value that must be a number. If the example value is omitted, a V3 Random number generator will be used.
`string`	example: string	Value that must be a string.
`regex`	pattern, example: string	Value that must match the given regular expression.
`equal`	example	Value that must be equal to the example. This is mainly used to reset the matching rules which cascade.
`timestamp`	format: string, example?: string	String value that must match the provided datetime format string. See Java SimpleDateFormat for details on the format string. If the example value is omitted, a value will be generated using a Timestamp generator and the current system date and time.
`time`	format: string, example?: string	String value that must match the provided time format string. See Java SimpleDateFormat for details on the format string. If the example value is omitted, a value will be generated using a Time generator and the current system time.
`date`	format: string, example?: string	String value that must match the provided date format string. See Java SimpleDateFormat for details on the format string. If the example value is omitted, a value will be generated using a Date generator and the current system date.
`includes`	value: string	Value that must include the example value as a substring.
`nullValue`		Value that must be null. This will only match the JSON Null value. For other content types, it will match if the attribute is missing.
`arrayContaining`	variants...	Matches the items in an array against a number of variants. Matching is successful if each variant occurs once in the array. Variants may be objects containing matching rules.
`eachKeyLike`	key: string, template: any	Object where the keys itself is ignored, but the values must match a particular shape. Variants may be objects containing matching rules
`fromProviderState`	expression: string, exampleValue: string	Sets a type matcher and a provider state generator. See the section below.

Array contains matcher

The array contains matcher function allows you to match the actual list against a list of required variants. These work by matching each item against each of the variants, and the matching succeeds if each variant matches at least one item. Order of items in the list is not important.

The variants can have a totally different structure, and can have their own matching rules to apply. For an example of how these can be used to match a hypermedia format like Siren, see Example Pact + Siren project.

function	description
`arrayContaining`	Matches the items in an array against a number of variants. Matching is successful if each variant occurs once in the array. Variants may be objects containing matching rules.

{
  "actions": arrayContaining(
    {
      "name": "update",
      "method": "PUT",
      "href": url("http://localhost:9000", ["orders", regex("\\d+", "1234")])
    },
    {
      "name": "delete",
      "method": "DELETE",
      "href": url("http://localhost:9000", ["orders", regex("\\d+", "1234")])
    }
  )
}

Provider State Injected Values

The fromProviderState matching function allows values to be generated based on values returned from the provider state callbacks. This should be used for the cases were database entries have auto-generated values and these values need to be used in the URLs or query parameters.

For an example, see examples/v3/provider-state-injected.

For this to work, in the consumer test we use the fromProviderState matching function which takes an expression and an example value. The example value will be used in the consumer test.

For example:

  query: { accountNumber: fromProviderState("\${accountNumber}", "100") },

Then when the provider is verified, the provider state callback can return a map of values. These values will be used to generate the value using the expression supplied from the consumer test.

For example:

stateHandlers: {
  "Account Test001 exists": (params) => {
    const account = new Account(0, 0, "Test001", params.accountRef, new AccountNumber(0), Date.now(), Date.now())
    const persistedAccount = accountRepository.save(account)
    return { accountNumber: persistedAccount.accountNumber.id }
  }
},

A note about typescript

Because of the way interfaces work in typescript, if you are passing a typed object to a matcher, and that type is an interface (say Foo):

interface Foo {
  a: string;
}

const f: Foo = { a: "broken example" };


provider.addInteraction({
  uponReceiving: "a post with foo",
  withRequest: {
    method: "POST",
    path: "/",
    body: like(f) // Type 'Matcher<Foo>' is not assignable to type 'AnyTemplate'.
  },
  ...
})

then you may run into the following message:

Type 'Matcher<Foo>' is not assignable to type 'AnyTemplate'.

This is one of the rare places where type differs from interface. You have two options:

Use type Foo = { instead of interface Foo {
If this is not possible, Pact exports a workaround wrapper type called InterfaceToTemplate<YourTypeHere>. Use it like this:
```
const f: InterfaceToTemplate<Foo> = { a: "working example" };
```

Matching Packages​

V2 Matching rules​

Match common formats​

Match based on type​

Match based on arrays​

Match by regular expression​

V3 Matching rules​

Array contains matcher​

Provider State Injected Values​

A note about typescript​

Matching Packages

V2 Matching rules

Match common formats

Match based on type

Match based on arrays

Match by regular expression

V3 Matching rules

Array contains matcher

Provider State Injected Values

A note about typescript