Move kubeconfig utility to a shared pkg

Signed-off-by: Ahmet Alp Balkan <ahmetb@google.com>

internal/kubeconfig/contexts_test.go

@@ -0,0 +1,77 @@
+package kubeconfig
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+func TestKubeconfig_ContextNames(t *testing.T) {
+	tl := &testLoader{in: strings.NewReader(`
+contexts:
+- name: abc
+- name: def
+  field1: value1
+- name: ghi
+  foo:
+    bar: zoo`)}
+
+	kc := new(Kubeconfig).WithLoader(tl)
+	if err := kc.Parse(); err != nil {
+		t.Fatal(err)
+	}
+
+	ctx := kc.ContextNames()
+	expected := []string{"abc", "def", "ghi"}
+	if diff := cmp.Diff(expected, ctx); diff != "" {
+		t.Fatalf("%s", diff)
+	}
+}
+
+func TestKubeconfig_ContextNames_noContextsEntry(t *testing.T) {
+	tl := &testLoader{in: strings.NewReader(`a: b`)}
+	kc := new(Kubeconfig).WithLoader(tl)
+	if err := kc.Parse(); err != nil {
+		t.Fatal(err)
+	}
+	ctx := kc.ContextNames()
+	var expected []string = nil
+	if diff := cmp.Diff(expected, ctx); diff != "" {
+		t.Fatalf("%s", diff)
+	}
+}
+
+func TestKubeconfig_ContextNames_nonArrayContextsEntry(t *testing.T) {
+	tl := &testLoader{in: strings.NewReader(`contexts: "hello"`)}
+	kc := new(Kubeconfig).WithLoader(tl)
+	if err := kc.Parse(); err != nil {
+		t.Fatal(err)
+	}
+	ctx := kc.ContextNames()
+	var expected []string = nil
+	if diff := cmp.Diff(expected, ctx); diff != "" {
+		t.Fatalf("%s", diff)
+	}
+}
+
+func TestKubeconfig_CheckContextExists(t *testing.T) {
+	tl := &testLoader{in: strings.NewReader(`contexts:
+- name: c1
+- name: c2`)}
+
+	kc := new(Kubeconfig).WithLoader(tl)
+	if err := kc.Parse(); err != nil {
+		t.Fatal(err)
+	}
+
+	if !kc.ContextExists("c1") {
+		t.Fatal("c1 actually exists; reported false")
+	}
+	if !kc.ContextExists("c2") {
+		t.Fatal("c2 actually exists; reported false")
+	}
+	if kc.ContextExists("c3") {
+		t.Fatal("c3 does not exist; but reported true")
+	}
+}