Add more unit tests for using non-exist key of an object in task step

Prior to this commit, the validation exists to check if individual keys
of an object param being used in task steps indeed exist, but the test
was missed.

In this PR, we add the unit test for that.

pkg/apis/pipeline/v1/task_validation_test.go

@@ -987,6 +987,28 @@ func TestTaskSpecValidateError(t *testing.T) {
 			Message: `variable type invalid in "$(params.gitrepo[*])"`,
 			Paths:   []string{"steps[0].args[0]"},
 		},
+	}, {
+		name: "non-existent individual key of an object param is used in task step",
+		fields: fields{
+			Params: []v1.ParamSpec{{
+				Name: "gitrepo",
+				Type: v1.ParamTypeObject,
+				Properties: map[string]v1.PropertySpec{
+					"url":    {},
+					"commit": {},
+				},
+			}},
+			Steps: []v1.Step{{
+				Name:       "do-the-clone",
+				Image:      "some-git-image",
+				Args:       []string{"$(params.gitrepo.non-exist-key)"},
+				WorkingDir: "/foo/bar/src/",
+			}},
+		},
+		expectedError: apis.FieldError{
+			Message: `non-existent variable in "$(params.gitrepo.non-exist-key)"`,
+			Paths:   []string{"steps[0].args[0]"},
+		},
 	}, {
 		name: "Inexistent param variable in volumeMount with existing",
 		fields: fields{

pkg/apis/pipeline/v1beta1/task_validation_test.go

@@ -1099,6 +1099,28 @@ func TestTaskSpecValidateError(t *testing.T) {
 			Message: `variable type invalid in "$(params.gitrepo[*])"`,
 			Paths:   []string{"steps[0].args[0]"},
 		},
+	}, {
+		name: "non-existent individual key of an object param is used in task step",
+		fields: fields{
+			Params: []v1beta1.ParamSpec{{
+				Name: "gitrepo",
+				Type: v1beta1.ParamTypeObject,
+				Properties: map[string]v1beta1.PropertySpec{
+					"url":    {},
+					"commit": {},
+				},
+			}},
+			Steps: []v1beta1.Step{{
+				Name:       "do-the-clone",
+				Image:      "some-git-image",
+				Args:       []string{"$(params.gitrepo.non-exist-key)"},
+				WorkingDir: "/foo/bar/src/",
+			}},
+		},
+		expectedError: apis.FieldError{
+			Message: `non-existent variable in "$(params.gitrepo.non-exist-key)"`,
+			Paths:   []string{"steps[0].args[0]"},
+		},
 	}, {
 		name: "Inexistent param variable in volumeMount with existing",
 		fields: fields{