kinbiko / jsonassert

It's difficult to confirm that a JSON payload, e.g. a HTTP request or response body, does indeed look the way you want using the built-in Go testing package. jsonassert is an easy-to-use Go test assertion library for verifying that two representations of JSON are semantically equal.

Usage

Create a new *jsonassert.Asserter in your test and use this to make assertions against your JSON payloads:

func TestWhatever(t *testing.T) {
	ja := jsonassert.New(t)
	// find some sort of payload
	name := "River Tam"
	age := 16
	ja.Assertf(payload, `
	{
		"name": "%s",
		"age": %d,
		"averageTestScore": "%s",
		"skills": [
			{ "name": "martial arts", "level": 99 },
			{ "name": "intelligence", "level": 100 },
			{ "name": "mental fortitude", "level": 4 }
		]
	}`, name, age, "99%")
}

You may pass in fmt.Sprintf arguments after the expected JSON structure. This feature may be useful for the case when you already have variables in your test with the expected data or when your expected JSON contains a % character which could be misinterpreted as a format directive.

ja.Assertf() supports assertions against strings only.

Check for presence only

Some properties of a JSON payload may be difficult to know in advance. E.g. timestamps, UUIDs, or other randomly assigned values.

For these types of values, place the string "<<PRESENCE>>" as the expected value, and jsonassert will only verify that this key exists (i.e. the actual JSON has the expected key, and its value is not null), but this does not check its value.

For example:

func TestWhatever(t *testing.T) {
	ja := jsonassert.New(t)
	ja.Assertf(`
	{
		"time": "2019-01-28T21:19:42",
		"uuid": "94ae1a31-63b2-4a55-a478-47764b60c56b"
	}`, `
	{
		"time": "<<PRESENCE>>",
		"uuid": "<<PRESENCE>>"
	}`)
}

The above will pass your test, but:

func TestWhatever(t *testing.T) {
	ja := jsonassert.New(t)
	ja.Assertf(`
	{
		"date": "2019-01-28T21:19:42",
		"uuid": null
	}`, `
	{
		"time": "<<PRESENCE>>",
		"uuid": "<<PRESENCE>>"
	}`)
}

The above will fail your tests because the time key was not present in the actual JSON, and the uuid was null.

Ignore ordering in arrays

If your JSON payload contains an array with elements whose ordering is not deterministic, then you can use the "<<UNORDERED>>" directive as the first element of the array in question:

func TestUnorderedArray(t *testing.T) {
	ja := jsonassert.New(t)
	payload := `["bar", "foo", "baz"]`
	ja.Assertf(payload, `["foo", "bar", "baz"]`)                  // Order matters, will fail your test.
	ja.Assertf(payload, `["<<UNORDERED>>", "foo", "bar", "baz"]`) // Order agnostic, will pass your test.
}

Docs

You can find the GoDocs for this package here.

Contributing

Contributions are welcome. Please read the contribution guidelines and discuss feature requests in an issue before opening a PR.