Re-add the test for Uname on GOOS=linux

probe/host/system_linux.go

@@ -9,6 +9,9 @@ import (
 	"time"
 )
 
+// Uname is swappable for mocking in tests.
+var Uname = syscall.Uname
+
 func charsToString(ca [65]int8) string {
 	s := make([]byte, len(ca))
 	var lens int
@@ -24,7 +27,7 @@ func charsToString(ca [65]int8) string {
 // GetKernelVersion returns the kernel version as reported by uname.
 var GetKernelVersion = func() (string, error) {
 	var utsname syscall.Utsname
-	if err := syscall.Uname(&utsname); err != nil {
+	if err := Uname(&utsname); err != nil {
 		return "unknown", err
 	}
 	return fmt.Sprintf("%s %s", charsToString(utsname.Release), charsToString(utsname.Version)), nil

probe/host/system_linux_test.go

@@ -0,0 +1,40 @@
+package host_test
+
+import (
+	"fmt"
+	"syscall"
+	"testing"
+
+	"github.com/weaveworks/scope/probe/host"
+)
+
+func TestUname(t *testing.T) {
+	oldUname := host.Uname
+	defer func() { host.Uname = oldUname }()
+
+	const (
+		release = "rls"
+		version = "ver"
+	)
+	host.Uname = func(uts *syscall.Utsname) error {
+		uts.Release = string2c(release)
+		uts.Version = string2c(version)
+		return nil
+	}
+
+	have, err := host.GetKernelVersion()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if want := fmt.Sprintf("%s %s", release, version); want != have {
+		t.Errorf("want %q, have %q", want, have)
+	}
+}
+
+func string2c(s string) [65]int8 {
+	var result [65]int8
+	for i, c := range s {
+		result[i] = int8(c)
+	}
+	return result
+}