| Unit testing is an important part of writing principled Go programs. The `testing` package provides the tools we need to write unit tests and the `go test` command runs tests. | ||
| For the sake of demonstration, this code is in package `main`, but it could be any package. Testing code typically lives in the same package as the code it tests. | package main |
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import ( |
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"fmt" |
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"testing" |
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) |
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| We'll be testing this simple implementation of an integer minimum. Typically, the code we're testing would be in a source file named something like `intutils.go`, and the test file for it would then be named `intutils_test.go`. | func IntMin(a, b int) int { |
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if a < b { |
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return a |
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} |
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return b |
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} |
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| A test is created by writing a function with a name beginning with `Test`. | func TestIntMinBasic(t *testing.T) { |
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ans := IntMin(2, -2) |
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if ans != -2 { |
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| `t.Error*` will report test failures but continue executing the test. `t.Fail*` will report test failures and stop the test immediately. | t.Errorf("IntMin(2, -2) = %d; want -2", ans) |
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} |
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} |
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| Writing tests can be repetitive, so it's idiomatic to use a *table-driven style*, where test inputs and expected outputs are listed in a table and a single loop walks over them and performs the test logic. | func TestIntMinTableDriven(t *testing.T) { |
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var tests = []struct { |
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a, b int |
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want int |
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}{ |
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{0, 1, 0}, |
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{1, 0, 0}, |
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{2, -2, -2}, |
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{0, -1, -1}, |
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{-1, 0, -1}, |
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} |
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for _, tt := range tests { |
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| t.Run enables running "subtests", one for each table entry. These are shown separately when executing `go test -v`. | testname := fmt.Sprintf("%d,%d", tt.a, tt.b) |
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t.Run(testname, func(t *testing.T) { |
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ans := IntMin(tt.a, tt.b) |
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if ans != tt.want { |
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t.Errorf("got %d, want %d", ans, tt.want) |
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} |
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}) |
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} |
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} |