Go by Example: Testing
+ +|
+ Unit testing is an important part of writing
+principled Go programs. The |
+ + + + | +
|
+ For the sake of demonstration, this code is in package
+ |
+
+  
+ package main
+ |
+
| + + | +
+
+ import (
+ "fmt"
+ "testing"
+)
+ |
+
|
+ 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
+ |
+
+
+ func IntMin(a, b int) int {
+ if a < b {
+ return a
+ } else {
+ return b
+ }
+}
+ |
+
|
+ A test is created by writing a function with a name
+beginning with |
+
+
+ func TestIntMinBasic(t *testing.T) {
+ ans := IntMin(2, -2)
+ if ans != -2 {
+ |
+
|
+
|
+
+
+ t.Errorf("IntMin(2, -2) = %d; want -2", ans)
+ }
+}
+ |
+
|
+ 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) {
+ var tests = []struct {
+ a, b int
+ want int
+ }{
+ {0, 1, 0},
+ {1, 0, 0},
+ {2, -2, -2},
+ {0, -1, -1},
+ {-1, 0, -1},
+ }
+ |
+
|
+ t.Run enables running “subtests”, one for each
+table entry. These are shown separately
+when executing |
+
+
+ for _, tt := range tests {
+ |
+
| + + | +
+
+ testname := fmt.Sprintf("%d,%d", tt.a, tt.b)
+ t.Run(testname, func(t *testing.T) {
+ ans := IntMin(tt.a, tt.b)
+ if ans != tt.want {
+ t.Errorf("got %d, want %d", ans, tt.want)
+ }
+ })
+ }
+}
+ |
+
|
+ Run all tests in the current project in verbose mode. + + |
+
+
+ $ go test -v
+== RUN TestIntMinBasic
+--- PASS: TestIntMinBasic (0.00s)
+=== RUN TestIntMinTableDriven
+=== RUN TestIntMinTableDriven/0,1
+=== RUN TestIntMinTableDriven/1,0
+=== RUN TestIntMinTableDriven/2,-2
+=== RUN TestIntMinTableDriven/0,-1
+=== RUN TestIntMinTableDriven/-1,0
+--- PASS: TestIntMinTableDriven (0.00s)
+ --- PASS: TestIntMinTableDriven/0,1 (0.00s)
+ --- PASS: TestIntMinTableDriven/1,0 (0.00s)
+ --- PASS: TestIntMinTableDriven/2,-2 (0.00s)
+ --- PASS: TestIntMinTableDriven/0,-1 (0.00s)
+ --- PASS: TestIntMinTableDriven/-1,0 (0.00s)
+PASS
+ok examples/testing 0.023s
+ |
+
+ Next example: Command-Line Arguments. +
+ + +