test: make token exchange settable so it can be tested, add test

Signed-off-by: Chris Privitere <23177737+cprivitere@users.noreply.github.com>

Author: cprivitere

internal/emlb/emlb.go

@@ -51,6 +51,8 @@ const (
 	loadBalancerOriginIDAnnotation = "equinix.com/loadbalanceroriginID"
 	// EMLBVIPID is the stringused to refer to the EMLB load balancer and VIP Manager type.
 	EMLBVIPID = "EMLB"
+	// loadbalancerTokenExchangeURL is the default URL to use for Token Exchange to talk to the Equinix Metal Load Balancer API
+	loadbalancerTokenExchnageURL = "https://iam.metalctrl.io/api-keys/exchange" //nolint:gosec
 )
 
 var lbMetros = map[string]string{
@@ -87,8 +89,9 @@ func NewEMLB(metalAPIKey, projectID, metro string) *EMLB {
 
 	manager.client = lbaas.NewAPIClient(emlbConfig)
 	manager.tokenExchanger = &TokenExchanger{
-		metalAPIKey: metalAPIKey,
-		client:      manager.client.GetConfig().HTTPClient,
+		metalAPIKey:      metalAPIKey,
+		tokenExchangeURL: loadbalancerTokenExchnageURL,
+		client:           manager.client.GetConfig().HTTPClient,
 	}
 	manager.projectID = projectID
 	manager.metro = metro

internal/emlb/token-exchanger_test.go

@@ -0,0 +1,57 @@
+/*
+Copyright 2024 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package emlb
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestTokenExchanger_Token(t *testing.T) {
+	// Create a mock server to handle the token exchange request
+	mockServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// Return a sample token response
+		response := `{"access_token": "sample_token", "expires_in": 3600}`
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte(response))
+	}))
+	defer mockServer.Close()
+
+	// Create a TokenExchanger instance with the mock server URL
+	exchanger := &TokenExchanger{
+		metalAPIKey:      "sample_api_key",
+		tokenExchangeURL: mockServer.URL,
+		client:           mockServer.Client(),
+	}
+
+	// Call the Token method
+	token, err := exchanger.Token()
+
+	// Assert that no error occurred
+	assert.NoError(t, err)
+
+	// Assert that the token is not nil
+	assert.NotNil(t, token)
+
+	// Assert the token values
+	assert.Equal(t, "sample_token", token.AccessToken)
+	assert.Equal(t, time.Now().Add(time.Hour).Round(time.Second), token.Expiry.Round(time.Second))
+}

internal/emlb/token_exchanger.go

@@ -28,14 +28,14 @@ import (
 
 // TokenExchanger is an client for authenticating to the Load Balancer API.
 type TokenExchanger struct {
-	metalAPIKey string
-	client      *http.Client
+	metalAPIKey      string
+	tokenExchangeURL string
+	client           *http.Client
 }
 
 // Token creates a Token object to authenticate with the Load Balancer API.
 func (m *TokenExchanger) Token() (*oauth2.Token, error) {
-	tokenExchangeURL := "https://iam.metalctrl.io/api-keys/exchange"                             //nolint:gosec
-	tokenExchangeRequest, err := http.NewRequest(http.MethodPost, tokenExchangeURL, http.NoBody) //nolint:noctx // we can't find a way to get the ctx into here yet and just using context.Background adds no value that we can tell
+	tokenExchangeRequest, err := http.NewRequest(http.MethodPost, m.tokenExchangeURL, http.NoBody) //nolint:noctx // we can't find a way to get the ctx into here yet and just using context.Background adds no value that we can tell
 	if err != nil {
 		return nil, err
 	}