GO-001 Prefer Table-Driven Tests

Express related test-cases as data to keep tests readable and exhaustive, and compare the results using full-structure comparison.

Table-driven tests express each case as a row of data, keeping intent obvious and making it cheap to add cases.

Why this matters

Table-driven tests improve code maintainability and test coverage by separating test logic from test data. This approach makes it trivial to add new test cases; simply add a row to the data structure without duplicating test logic. It also enhances readability by presenting all test scenarios in a clear, tabular format, making it easier to spot missing cases or inconsistencies.

Additionally, table-driven tests scale better as your test suite grows, reduce oilerplate code, and make failures more descriptive by automatically including the test case name in output.

Example

func TestAbs(t *testing.T) {
  t.Parallel()

  testCases := []struct {
    name string
    in   int
    want int
  }{
    {
      name: "Positive",
      in:   3,
      want: 3,
    }, {
      name: "Negative",
      in:   -3,
      want: 3,
    }, {
      name: "Zero",
      in: 0,
      want: 0,
    },
  }
  for _, tc := range testCases {
    t.Run(tc.name, func(t *testing.T) {
      // Act
      v := math.Abs(tc.in)

      // Assert
      if got, want := v, tc.want; got != want {
        t.Errorf("Abs(%d) = %d, want %d", tc.in, got, want)
      }
    })
  }
}