assert.markdown
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# Assert
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Stability: 5 - Locked
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This module is used for writing unit tests for your applications, you can
access it with `require('assert')`.
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## assert.fail(actual, expected, message, operator)
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Throws an exception that displays the values for `actual` and `expected` separated by the provided operator.
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## assert(value, message), assert.ok(value[, message])
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Tests if value is truthy, it is equivalent to `assert.equal(true, !!value, message);`
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## assert.equal(actual, expected[, message])
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Tests shallow, coercive equality with the equal comparison operator ( `==` ).
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## assert.notEqual(actual, expected[, message])
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Tests shallow, coercive non-equality with the not equal comparison operator ( `!=` ).
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## assert.deepEqual(actual, expected[, message])
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Tests for deep equality.
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## assert.notDeepEqual(actual, expected[, message])
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Tests for any deep inequality.
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## assert.strictEqual(actual, expected[, message])
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Tests strict equality, as determined by the strict equality operator ( `===` )
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## assert.notStrictEqual(actual, expected[, message])
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Tests strict non-equality, as determined by the strict not equal operator ( `!==` )
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## assert.throws(block[, error]\[, message])
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Expects `block` to throw an error. `error` can be constructor, `RegExp` or
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validation function.
Validate instanceof using constructor:
assert.throws(
function() {
throw new Error("Wrong value");
},
Error
);
Validate error message using RegExp:
assert.throws(
function() {
throw new Error("Wrong value");
},
/value/
);
Custom error validation:
assert.throws(
function() {
throw new Error("Wrong value");
},
function(err) {
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if ( (err instanceof Error) && /value/.test(err) ) {
return true;
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}
},
"unexpected error"
);
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## assert.doesNotThrow(block[, message])
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Expects `block` not to throw an error, see `assert.throws` for details.
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## assert.ifError(value)
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Tests if value is not a false value, throws if it is a true value. Useful when
testing the first argument, `error` in callbacks.