adm upgrade status: add fixture test

pkg/cli/admin/upgrade/status/examples/README.md

@@ -0,0 +1,20 @@
+# Examples for `oc adm upgrade status`
+
+Each example consists of two inputs and one output, matched by a common substring:
+1. `TESTCASE-cv.yaml`(input): ClusterVersion object (created by `oc get clusterversion version -o yaml`)
+2. `TESTCASE-co.yaml`(input): list of ClusterOperators (created by `oc get clusteroperators -o yaml`)
+3. `TESTCASE.out`(output): expected output of `oc adm upgrade status` for the two outputs
+
+The `TestExamples` test in `examples_test.go` file above validates all examples. When the testcase
+is executed with a non-empty `UPDATE` environmental variable, it will update the `TESTCASE.out`
+fixture:
+
+```console
+$ UPDATE=yes go test -v ./pkg/cli/admin/upgrade/status/...
+```
+
+You can also pass the inputs to the `oc adm upgrade status` directly:
+
+```
+$ oc adm upgrade status --mock-clusterversion=not-upgrading-cv.yaml --mock-clusteroperators=not-upgrading-co.yaml
+```