add unit test for Contains

Signed-off-by: Zhou Hao <zhouhao@cn.fujitsu.com>

util/pkg/slice/BUILD.bazel

@@ -1,8 +1,14 @@
-load("@io_bazel_rules_go//go:def.bzl", "go_library")
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
 
 go_library(
     name = "go_default_library",
     srcs = ["slice.go"],
     importpath = "k8s.io/kops/util/pkg/slice",
     visibility = ["//visibility:public"],
 )
+
+go_test(
+    name = "go_default_test",
+    srcs = ["slice_test.go"],
+    embed = [":go_default_library"],
+)

util/pkg/slice/slice_test.go

@@ -45,3 +45,28 @@ func TestGetUniqueStrings(t *testing.T) {
 		}
 	}
 }
+
+func TestContains(t *testing.T) {
+	tests := []struct {
+		listStr  []string
+		e        string
+		contains bool
+	}{
+		{
+			listStr:  []string{"a", "b"},
+			e:        "a",
+			contains: true,
+		},
+		{
+			listStr:  []string{"a", "b"},
+			e:        "c",
+			contains: false,
+		},
+	}
+	for _, test := range tests {
+		contains := Contains(test.listStr, test.e)
+		if test.contains != contains {
+			t.Errorf("Expected %v, got %v", test.contains, contains)
+		}
+	}
+}