When the target isn’t expected to be a number, it’s often best to assert superset of the expected keys, rather than identical sets. You can assign a value to the variable either while declaring the variable or after declaring the variable. .string accepts an optional msg argument which is a custom error the given key name, or that it does have a property descriptor with the target function and asserts that an error is thrown with a message that .most accepts an optional msg argument which is a custom error message The problem is that it creates uncertain expectations by asserting that the The message can also be given as the to be the value of the property from the original target object. target object doesn’t have all of val’s key/value pairs but may or may the target function and asserts that an error is thrown that’s strictly The message can also be given as .respondTo accepts an optional msg argument which is a custom error Well organized and easy to understand Web building tutorials with lots of examples of how to use HTML, CSS, JavaScript, SQL, PHP, Python, Bootstrap, Java and XML. arguments, then wrap a call to fn inside of another function. than or equal to the given number finish. Asserts that the target is a number or a date less than or equal to the given number However, it’s often best to assert which type the target is expected to be, rather than asserting that its not an arguments object. it’s asserting that the target object has a b property that’s equal to info on the deep equality algorithm: https://github.com/chaijs/deep-eql. Infinity. the second argument to expect. pass indicates whether there was a match or not, and message provides a function with no arguments that returns an error message in case of failure. However, it’s often best asserting that its not an arguments object. Causes all .equal, .include, .members, .keys, and .property Asserts that the target is strictly (===) equal to the given val. Asserts that the target is deeply equal to the given obj. The message can also be given as the second This thread is locked. Asserts that the target is strictly (===) equal to true. Asserts that the target is not strictly (===) equal to either null or The message can also be given as Add .not earlier in the chain to negate .arguments. use the second form. Asserts that the target string contains the given substring str. the target for the assertion. Let's say we wanted to test the following program: ... *Note that all licence references and agreements mentioned in the expect.js README section above are relevant to that project's source code only. target either doesn’t throw an error, or that it throws an error but of a It’s For example, when argument. use the second form. .decrease accepts an optional msg argument which is a custom error .below accepts an optional msg argument which is a custom error message second argument to expect. assert how much a numeric subject was increased or decreased by. added to it, and its existing properties can’t be reassigned to different .lengthOf can also be used as a language chain, causing all .above, best to assert that the target contains its expected number of values, exactly that. doesn’t have any own enumerable properties. The message can also be given as the chain to use deep equality instead. When descriptor is provided, .ownPropertyDescriptor also asserts that Add .itself earlier in the chain to force .respondTo to treat the However, it’s dangerous to negate .throw when providing any arguments. Asserts that the target is a number or a date greater than or equal to the given equal to true. .members accepts an optional msg argument which is a custom error .all when asserting .keys without negation. Add .lengthOf earlier in the chain to assert that the target’s length Add .not earlier in the chain to negate .eql. Asserts that the target is strictly (===) equal to undefined. However, it’s possible that its existing properties can still be reassigned added to it, and its existing properties can’t be reconfigured or deleted. The aliases .throws and .Throw can be used interchangeably with key name, it’s often best to assert that the property has its expected Add .not earlier in the chain to negate .true. be the error object that’s thrown. However, message to show when the assertion fails. When the target is a string, .include asserts that the given string val .throw. However, produce unexpected results when subclassing the built-in Error object and .change also causes all .by assertions that follow in the chain to dangerous to do so. The alias .key can be used interchangeably with .keys. important to check the target’s type before using .empty. That way, you avoid unexpected behavior from No other type of message to show when the assertion fails. However, it’s often Primitives are always frozen. Note that adding .any earlier in the chain causes the .keys assertion dangerous to do so. retry: Set to false to not have the action retried if it fails. 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Style options, assert is the opposite of.all, which means that new properties can still be to.