Add integration test for krew upgrade (#242)

* When looking up executables, return their location

* Add integration test for `krew upgrade`

* Do not return value from assertion method, expose lookup method instead

* Assert upgrade by real plugin path instead of plugin hash sum

This assumes that the actual plugin path changes from one version to another.

* Improve name of test helper `realLocation` -> `resolvePluginSymlink`

docs/CONTRIBUTOR_GUIDE.md

@@ -31,7 +31,7 @@ go get golang.org/x/tools/cmd/goimports
 and run:
 
 ```bash
-goimports -local sigs.k8s.io/krew -w cmd pkg test
+goimports -local sigs.k8s.io/krew -w cmd pkg integration_test
 ```
 
 In addition, a boilerplate license header is expected in all source files.

integration_test/testutil_test.go

@@ -116,21 +116,20 @@ func lines(in []byte) []string {
 	return strings.Split(trimmed, "\n")
 }
 
-func (it *ITest) lookupExecutable(file string) error {
+func (it *ITest) LookupExecutable(file string) (string, error) {
 	orig := os.Getenv("PATH")
 	defer func() { os.Setenv("PATH", orig) }()
 
 	binPath := filepath.Join(it.Root(), "bin")
 	os.Setenv("PATH", binPath)
 
-	_, err := exec.LookPath(file)
-	return err
+	return exec.LookPath(file)
 }
 
 // AssertExecutableInPATH asserts that the executable file is in bin path.
 func (it *ITest) AssertExecutableInPATH(file string) {
 	it.t.Helper()
-	if err := it.lookupExecutable(file); err != nil {
+	if _, err := it.LookupExecutable(file); err != nil {
 		it.t.Fatalf("executable %s not in PATH: %+v", file, err)
 	}
 }
@@ -139,7 +138,7 @@ func (it *ITest) AssertExecutableInPATH(file string) {
 // path.
 func (it *ITest) AssertExecutableNotInPATH(file string) {
 	it.t.Helper()
-	if err := it.lookupExecutable(file); err == nil {
+	if _, err := it.LookupExecutable(file); err == nil {
 		it.t.Fatalf("executable %s still exists in PATH", file)
 	}
 }

integration_test/upgrade_test.go

@@ -14,4 +14,44 @@
 
 package integrationtest
 
-// TODO(ahmetb): implement upgrade tests (https://krew.dev/issues/233)
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"sigs.k8s.io/krew/pkg/constants"
+)
+
+func TestKrewUpgrade(t *testing.T) {
+	skipShort(t)
+
+	test, cleanup := NewTest(t)
+	defer cleanup()
+
+	test.WithIndex().
+		Krew("install", "--manifest", filepath.Join("testdata", validPlugin+constants.ManifestExtension)).
+		RunOrFail()
+	initialLocation := resolvePluginSymlink(test, validPlugin)
+
+	test.Krew("upgrade").RunOrFail()
+	eventualLocation := resolvePluginSymlink(test, validPlugin)
+
+	if initialLocation == eventualLocation {
+		t.Errorf("Expecting the plugin path to change but was the same.")
+	}
+}
+
+func resolvePluginSymlink(test *ITest, plugin string) string {
+	test.t.Helper()
+	linkToPlugin, err := test.LookupExecutable("kubectl-" + plugin)
+	if err != nil {
+		test.t.Fatal(err)
+	}
+
+	realLocation, err := os.Readlink(linkToPlugin)
+	if err != nil {
+		test.t.Fatal(err)
+	}
+
+	return realLocation
+}