The expect function is used every time you want to test a value.
You will rarely call expect by itself.
The value to apply matchers against.
Adds a module to format application-specific data structures for serialization.
Matches anything that was created with the given constructor.
You can use it inside toEqual or toBeCalledWith instead of a literal value.
Matches anything but null or undefined. You can use it inside toEqual or toBeCalledWith instead
of a literal value. For example, if you want to check that a mock function is called with a
non-null argument:
Matches any array made up entirely of elements in the provided array.
You can use it inside toEqual or toBeCalledWith instead of a literal value.
Optionally, you can provide a type for the elements via a generic.
Verifies that a certain number of assertions are called during a test. This is often useful when testing asynchronous code, in order to make sure that assertions in a callback actually got called.
You can use expect.extend to add your own matchers to Jest.
Verifies that at least one assertion is called during a test. This is often useful when testing asynchronous code, in order to make sure that assertions in a callback actually got called.
Matches any object that recursively matches the provided keys. This is often handy in conjunction with other asymmetric matchers.
Optionally, you can provide a type for the object via a generic. This ensures that the object contains the desired structure.
Matches any received string that contains the exact expected string
Matches any string that contains the exact provided string
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The
expectfunction is used every time you want to test a value. You will rarely callexpectby itself.