Go test <function> returns undefined: <function>

Question

Trying to run "go test sum_test.go" returns an error:

./sum_test.go:18:13: undefined: SumInt8 FAIL command-line-arguments [build failed]

I'm taking an introductory course in golang. Our teacher distributed a code-file, sum.go, and a testing-file, sum_test.go. Trying to run "go test" on sum_test.go returns the error above. The code runs fine on our teachers mac, and he's having difficulties recreating the problem. Here's my go environment settings: https://pastebin.com/HcuNVcAF

sum.go

package sum

func SumInt8(a, b int8) int8 {
  return a + b
}

func SumFloat64(a, b float64) float64 {
  return a + b
}

sum_test.go

package sum

import "testing"

// Check https://golang.org/ref/spec#Numeric_types and stress the limits!
var sum_tests_int8 = []struct{
  n1       int8
  n2       int8
  expected int8
}{
  {1, 2, 3},
  {4, 5, 9},
  {120, 1, 121},
}

func TestSumInt8(t *testing.T) {
for _, v := range sum_tests_int8 {
    if val := SumInt8(v.n1, v.n2); val != v.expected {
        t.Errorf("Sum(%d, %d) returned %d, expected %d", 
v.n1, v.n2, val, v.expected)
    }
  }
}

I see no particular errors, so I expected "go test sum_test.go" to run, and succeed. However it seems it can't find the method SumInt8 in sum.go.

The arguments to go test are packages, not files. This is the same as for the build and install commands. Try go test . or simply go test (or, if you really want to, list all files required to build the tests). — Peter

peterSO peterSO · Accepted Answer · 2019-02-08T12:19:26

$ go help packages
Many commands apply to a set of packages:
go action [packages]
Usually, [packages] is a list of import paths.

An import path that is a rooted path or that begins with a . or .. element is interpreted as a file system path and denotes the package in that directory.

Otherwise, the import path P denotes the package found in the directory DIR/src/P for some DIR listed in the GOPATH environment variable (For more details see: 'go help gopath').

If no import paths are given, the action applies to the package in the current directory.

As a special case, if the package list is a list of .go files from a single directory, the command is applied to a single synthesized package made up of exactly those files, ignoring any build constraints in those files and ignoring any other files in the directory.

List all the files in the current directory used in the test:

go test sum_test.go sum.go

or simply test the complete package in the current directory.

go test

For example,

$ go test -v sum_test.go sum.go
=== RUN   TestSumInt8
--- PASS: TestSumInt8 (0.00s)
PASS
ok      command-line-arguments  0.002s
$

or, for the complete package

$ go test -v
=== RUN   TestSumInt8
--- PASS: TestSumInt8 (0.00s)
PASS
ok      so/sum  0.002s
$

Option '-v' produces verbose output.

sum_test.go:

package sum

import "testing"

// Check https://golang.org/ref/spec#Numeric_types and stress the limits!
var sum_tests_int8 = []struct {
    n1       int8
    n2       int8
    expected int8
}{
    {1, 2, 3},
    {4, 5, 9},
    {120, 1, 121},
}

func TestSumInt8(t *testing.T) {
    for _, v := range sum_tests_int8 {
        if val := SumInt8(v.n1, v.n2); val != v.expected {
            t.Errorf("Sum(%d, %d) returned %d, expected %d",
                v.n1, v.n2, val, v.expected)
        }
    }
}

sum.go:

package sum

func SumInt8(a, b int8) int8 {
    return a + b
}

func SumFloat64(a, b float64) float64 {
    return a + b
}

Go test <function> returns undefined: <function>

1 Answers