test(azidentity): add unit test for doForClient function

The focus is on methods/behavior implemented by azidentity
package. I didn't aim to hit 100% coverage, mainly because
there are error paths determined by e.g. std http package etc.

Signed-off-by: HandsomeJack <[email protected]>

sdk/azidentity/azidentity_test.go

@@ -7,11 +7,14 @@
 package azidentity
 
 import (
+	"bytes"
 	"context"
 	"crypto/x509"
 	"errors"
 	"fmt"
+	"io"
 	"net/http"
+	"net/http/httptest"
 	"os"
 	"path/filepath"
 	"reflect"
@@ -22,13 +25,15 @@ import (
 	"github.com/Azure/azure-sdk-for-go/sdk/azcore"
 	"github.com/Azure/azure-sdk-for-go/sdk/azcore/cloud"
 	"github.com/Azure/azure-sdk-for-go/sdk/azcore/policy"
+	azruntime "github.com/Azure/azure-sdk-for-go/sdk/azcore/runtime"
 	"github.com/Azure/azure-sdk-for-go/sdk/azidentity/internal"
 	"github.com/Azure/azure-sdk-for-go/sdk/internal/mock"
 	"github.com/Azure/azure-sdk-for-go/sdk/internal/recording"
 	"github.com/AzureAD/microsoft-authentication-library-for-go/apps/cache"
 	"github.com/AzureAD/microsoft-authentication-library-for-go/apps/confidential"
 	"github.com/AzureAD/microsoft-authentication-library-for-go/apps/public"
 	"github.com/golang-jwt/jwt/v5"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
@@ -1001,6 +1006,107 @@ func TestTokenCachePersistenceOptions(t *testing.T) {
 	}
 }
 
+func TestDoForClient(t *testing.T) {
+	var (
+		policyHeaderName  = "PolicyHeader"
+		policyHeaderValue = "policyvalue"
+
+		reqBody  = []byte(`{"request": "azidentity"}`)
+		respBody = []byte(`{"response": "golang"}`)
+	)
+
+	tests := map[string]struct {
+		method  string
+		path    string
+		body    io.Reader
+		headers http.Header
+	}{
+		"happy path": {
+			method: http.MethodGet,
+			path:   "/foo/bar",
+			body:   bytes.NewBuffer(reqBody),
+			headers: http.Header{
+				"Header": []string{"value1", "value2"},
+			},
+		},
+		"no body": {
+			method: http.MethodGet,
+			path:   "/",
+			body:   http.NoBody,
+		},
+		"nil body": {
+			method: http.MethodGet,
+			path:   "/",
+			body:   nil,
+		},
+		"headers with empty value": {
+			method: http.MethodGet,
+			path:   "/",
+			body:   http.NoBody,
+			headers: http.Header{
+				"Header": nil,
+			},
+		},
+	}
+
+	client, err := azcore.NewClient(module, version, azruntime.PipelineOptions{
+		// add PerCall policy to ensure doForClient calls .Pipeline.Do()
+		PerCall: []policy.Policy{
+			policyFunc(func(req *policy.Request) (*http.Response, error) {
+				req.Raw().Header.Set(policyHeaderName, policyHeaderValue)
+				return req.Next()
+			}),
+		},
+	}, nil)
+	require.NoError(t, err)
+
+	for name, tt := range tests {
+		tt := tt
+
+		t.Run(name, func(t *testing.T) {
+			server := httptest.NewServer(http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
+				assert.Equal(t, tt.method, req.Method)
+				assert.Equal(t, tt.path, req.URL.Path)
+
+				rb, err := io.ReadAll(req.Body)
+				assert.NoError(t, err)
+
+				if tt.body != nil && tt.body != http.NoBody {
+					assert.Equal(t, string(reqBody), string(rb))
+				} else {
+					assert.Empty(t, rb)
+				}
+
+				assert.Equal(t, policyHeaderValue, req.Header.Get(policyHeaderName))
+
+				rw.Header().Set("content-type", "application/json")
+				_, err = rw.Write(respBody)
+				assert.NoError(t, err)
+			}))
+			defer server.Close()
+
+			req, err := http.NewRequestWithContext(context.Background(), tt.method, server.URL+tt.path, tt.body)
+			require.NoError(t, err)
+
+			for k, vs := range tt.headers {
+				for _, v := range vs {
+					req.Header.Add(k, v)
+				}
+			}
+
+			resp, err := doForClient(client, req)
+			require.NoError(t, err)
+			defer resp.Body.Close()
+
+			require.Equal(t, http.StatusOK, resp.StatusCode)
+
+			b, err := io.ReadAll(resp.Body)
+			require.NoError(t, err)
+			assert.Equal(t, string(respBody), string(b))
+		})
+	}
+}
+
 // ==================================================================================================================================
 
 type fakeConfidentialClient struct {
@@ -1098,3 +1204,12 @@ func (f fakePublicClient) AcquireTokenInteractive(ctx context.Context, scopes []
 }
 
 var _ msalPublicClient = (*fakePublicClient)(nil)
+
+// ==================================================================================================================================
+
+type policyFunc func(*policy.Request) (*http.Response, error)
+
+// Do implements the Policy interface on policyFunc.
+func (pf policyFunc) Do(req *policy.Request) (*http.Response, error) {
+	return pf(req)
+}