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Javascript does not equal or less than11/21/2023 ![]() Test authors can't turn on custom testers for certain assertions and turn them off for others (a custom matcher should be used instead if that behavior is desired). Other times, however, a test author may want to allow for some flexibility in their test, and toBeWithinRange may be a more appropriate assertion.Ĭustom equality testers are good for globally extending Jest matchers to apply custom equality logic for all equality comparisons. Sometimes a test author may want to assert two numbers are exactly equal and should use toBe. For example, the toBeWithinRange example in the expect.extend section is a good example of a custom matcher. A tester is a method used by matchers that do equality checks to determine if objects are the same.Ĭustom matchers are good to use when you want to provide a custom assertion that test authors can use in their tests. Matchers are methods available on expect, for example expect().toEqual(). See the example in the Recursive custom equality testers section for more details. If you use this function, pass through the custom testers your tester is given so further equality checks equals applies can also use custom testers the test author may have configured. It optionally takes a list of custom equality testers to apply to the deep equality checks. This is a deep-equality function that will return true if two objects have the same values (recursively). These helper functions and properties can be found on this inside a custom tester: this.equals(a, b, customTesters?) a class instance with fields a and b will not equal a literal object with fields a and b.Ĭustom testers are functions that return either the result ( true or false) of comparing the equality of the two given arguments or undefined if the tester does not handle the given objects and wants to delegate equality to other testers (for example, the builtin equality testers).Ĭustom testers are called with 3 arguments: the two objects to compare and the array of custom testers (used for recursive testers, see the section below).
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