don't forget to test the simple things

terraform/util_test.go

@@ -1,6 +1,8 @@
 package terraform
 
 import (
+	"fmt"
+	"reflect"
 	"testing"
 	"time"
 )
@@ -96,3 +98,44 @@ func TestUtilResourceProvider(t *testing.T) {
 		}
 	}
 }
+
+func TestUniqueStrings(t *testing.T) {
+	cases := []struct {
+		Input    []string
+		Expected []string
+	}{
+		{
+			[]string{},
+			[]string{},
+		},
+		{
+			[]string{"x"},
+			[]string{"x"},
+		},
+		{
+			[]string{"a", "b", "c"},
+			[]string{"a", "b", "c"},
+		},
+		{
+			[]string{"a", "a", "a"},
+			[]string{"a"},
+		},
+		{
+			[]string{"a", "b", "a", "b", "a", "a"},
+			[]string{"a", "b"},
+		},
+		{
+			[]string{"c", "b", "a", "c", "b"},
+			[]string{"a", "b", "c"},
+		},
+	}
+
+	for i, tc := range cases {
+		t.Run(fmt.Sprintf("unique-%d", i), func(t *testing.T) {
+			actual := uniqueStrings(tc.Input)
+			if !reflect.DeepEqual(tc.Expected, actual) {
+				t.Fatalf("Expected: %q\nGot: %q", tc.Expected, actual)
+			}
+		})
+	}
+}