# Go: Table-driven unit tests

Here is the code we want to test:

``````package search

// Find returns the smallest index i at which x <= a[i].
// If there is no such index, it returns len(a).
// The slice must be sorted in ascending order.
func Find(a []int, x int) int {
// binary search
i, j := 0, len(a)
for i < j {
m := i + (j-i)/2
// i ≤ m < j
if x > a[m] {
i = m + 1
} else {
j = m
}
}
return i
}``````
• Put the test code in a file whose name ends with _test.go.
• Write a function `TestXXX` with a single argument of type `*testing.T`. The test framework runs each such function.
• To indicate a failed test, call a failure function such as `t.Errorf`.
``````package search

import "testing"

var tests = []struct {
a   []int
x   int
exp int
}{
{[]int{}, 1, 0},
{[]int{1, 2, 3, 3}, 0, 0},
{[]int{1, 2, 3, 3}, 1, 0},
{[]int{1, 2, 3, 3}, 2, 1},
{[]int{1, 2, 3, 3}, 3, 3}, // Here's an error.
{[]int{1, 2, 3, 3}, 4, 4},
}

func TestFind(t *testing.T) {
for _, e := range tests {
res := Find(e.a, e.x)
if res != e.exp {
t.Errorf("Find(%v, %d) = %d, expected %d",
e.a, e.x, res, e.exp)
}
}
}``````

Run the tests with `go test`:

```\$ go test
--- FAIL: TestFind (0.00s)
search_test.go:22: Find([1 2 3 3], 3) = 2, expected 3
FAIL
exit status 1
FAIL    .../search      0.001s```