AssertEqual

assertEqual is a standard assertion used in many unit testing frameworks to verify that two values are equal. If the values compare equal, the test continues; if not, the framework signals a failure by raising an assertion error, often including a message showing the expected and actual values.

In Python's unittest, the method is self.assertEqual(first, second, msg=None). Here, first is the expected value and second the actual value; the assertion is complemented by methods like assertNotEqual, and other related checks. For floating point values, a specialized check such as assertAlmostEqual may be used with a tolerance to account for rounding errors.

In Java and JUnit, similar functionality is provided by Assert.assertEquals(expected, actual), with overloads for primitive types and objects, and optional custom failure messages. Other languages provide analogous checks under different names: NUnit’s Assert.AreEqual, R’s testthat::expect_equal, and many JavaScript testing frameworks use expect(actual).toEqual(expected) or similar constructs rather than a function named assertEqual.

Typical behavior across frameworks is consistent: on a successful match, tests proceed; on a mismatch, the test is marked as failed and a diagnostic message is produced, often showing the expected and actual values.

Common considerations include ensuring value-based equality rather than identity, handling mutable or nested structures appropriately, and addressing floating point comparisons with suitable tolerance. Developers should provide clear expected values and meaningful failure messages to aid debugging. While the exact API and naming vary by framework, the core purpose of assertEqual remains to verify that two values are equivalent in the tested context.