os: implement and smoketest os.Unsetenv

src/os/env_test.go

@@ -7,6 +7,7 @@ package os_test
 import (
 	. "os"
 	"reflect"
+	"strings"
 	"testing"
 )
 
@@ -20,6 +21,31 @@ func TestConsistentEnviron(t *testing.T) {
 	}
 }
 
+func TestUnsetenv(t *testing.T) {
+	const testKey = "GO_TEST_UNSETENV"
+	set := func() bool {
+		prefix := testKey + "="
+		for _, key := range Environ() {
+			if strings.HasPrefix(key, prefix) {
+				return true
+			}
+		}
+		return false
+	}
+	if err := Setenv(testKey, "1"); err != nil {
+		t.Fatalf("Setenv: %v", err)
+	}
+	if !set() {
+		t.Error("Setenv didn't set TestUnsetenv")
+	}
+	if err := Unsetenv(testKey); err != nil {
+		t.Fatalf("Unsetenv: %v", err)
+	}
+	if set() {
+		t.Fatal("Unsetenv didn't clear TestUnsetenv")
+	}
+}
+
 func TestLookupEnv(t *testing.T) {
 	const smallpox = "SMALLPOX"      // No one has smallpox.
 	value, ok := LookupEnv(smallpox) // Should not exist.