Refactor test oidc provider into its own package

This makes it easier to test other OIDC code.

plugin/pkg/client/auth/oidc/oidc_test.go

@@ -0,0 +1,75 @@
+package oidc
+
+import (
+	"testing"
+
+	"k8s.io/kubernetes/pkg/util/diff"
+
+	"github.com/coreos/go-oidc/jose"
+)
+
+func TestNewOIDCAuthProvider(t *testing.T) {
+	tests := []struct {
+		cfg map[string]string
+
+		wantErr            bool
+		wantInitialIDToken jose.JWT
+	}{
+		{
+			cfg: map[string]string{
+				cfgIssuerUrl: "auth.example.com",
+			},
+		},
+	}
+
+	for i, tt := range tests {
+		ap, err := newOIDCAuthProvider("cluster.example.com", tt.cfg, nil)
+		if tt.wantErr {
+			if err == nil {
+				t.Errorf("case %d: want non-nil err", i)
+				continue
+			}
+		}
+
+		if err != nil {
+			t.Errorf("case %d: unexpected error on newOIDCAuthProvider: %v", i, err)
+			continue
+		}
+
+		oidcAP, ok := ap.(*oidcAuthProvider)
+		if !ok {
+			t.Errorf("case %d: expected ap to be an oidcAuthProvider", i)
+			continue
+		}
+
+		if diff := compareJWTs(tt.wantInitialIDToken, oidcAP.initialIDToken); diff != "" {
+			t.Errorf("case %d: compareJWTs(tt.wantInitialIDToken, oidcAP.initialIDToken)=%v", i, diff)
+		}
+	}
+}
+
+func compareJWTs(a, b jose.JWT) string {
+	if a.Encode() == b.Encode() {
+		return ""
+	}
+
+	var aClaims, bClaims jose.Claims
+	for _, j := range []struct {
+		claims *jose.Claims
+		jwt    jose.JWT
+	}{
+		{&aClaims, a},
+		{&bClaims, b},
+	} {
+		var err error
+		*j.claims, err = j.jwt.Claims()
+		if err != nil {
+			*j.claims = jose.Claims(map[string]interface{}{
+				"msg": "bad claims",
+				"err": err,
+			})
+		}
+	}
+
+	return diff.ObjectDiff(a, b)
+}