update Managed Identity credential Test (Azure#17389)

Author: g2vinay

sdk/identity/azure-identity/src/main/java/com/azure/identity/ArcIdentityCredential.java

@@ -42,7 +42,7 @@ class ArcIdentityCredential extends ManagedIdentityServiceCredential {
      * @return A publisher that emits an {@link AccessToken}.
      */
     public Mono<AccessToken> authenticate(TokenRequestContext request) {
-        if  (getClientId() == null) {
+        if  (getClientId() != null) {
             return Mono.error(logger.logExceptionAsError(new ClientAuthenticationException(
                 "User assigned identity is not supported by the Azure Arc Managed Identity Endpoint. To authenticate "
                     + "with the system assigned identity omit the client id when constructing the"

sdk/identity/azure-identity/src/main/java/com/azure/identity/ManagedIdentityCredential.java

@@ -43,12 +43,12 @@ public final class ManagedIdentityCredential implements TokenCredential {
             managedIdentityServiceCredential = new AppServiceMsiCredential(clientId, identityClient);
         } else if (configuration.contains(Configuration.PROPERTY_IDENTITY_ENDPOINT)) {
             if (configuration.contains(Configuration.PROPERTY_IDENTITY_HEADER)) {
-                if (configuration.contains(PROPERTY_IDENTITY_SERVER_THUMBPRINT)) {
+                if (configuration.get(PROPERTY_IDENTITY_SERVER_THUMBPRINT) != null) {
                     managedIdentityServiceCredential = new ServiceFabricMsiCredential(clientId, identityClient);
                 } else {
                     managedIdentityServiceCredential = new VirtualMachineMsiCredential(clientId, identityClient);
                 }
-            } else if (configuration.contains(PROPERTY_IMDS_ENDPOINT)) {
+            } else if (configuration.get(PROPERTY_IMDS_ENDPOINT) != null) {
                 managedIdentityServiceCredential = new ArcIdentityCredential(clientId, identityClient);
             } else {
                 managedIdentityServiceCredential = new VirtualMachineMsiCredential(clientId, identityClient);

sdk/identity/azure-identity/src/test/java/com/azure/identity/ManagedIdentityCredentialTest.java

@@ -4,6 +4,7 @@
 package com.azure.identity;
 
 import com.azure.core.credential.TokenRequestContext;
+import com.azure.core.exception.ClientAuthenticationException;
 import com.azure.core.util.Configuration;
 import com.azure.identity.implementation.IdentityClient;
 import com.azure.identity.util.TestUtils;
@@ -86,4 +87,24 @@ public void testIMDS() throws Exception {
                         && expiresOn.getSecond() == token.getExpiresAt().getSecond())
                 .verifyComplete();
     }
+
+    @Test
+    public void testArcUserAssigned() throws Exception {
+        Configuration configuration = Configuration.getGlobalConfiguration().clone();
+
+        // setup
+        String token1 = "token1";
+        String endpoint = "http://localhost";
+        TokenRequestContext request = new TokenRequestContext().addScopes("https://management.azure.com");
+        configuration.put("IDENTITY_ENDPOINT", endpoint);
+        configuration.put("IMDS_ENDPOINT", endpoint);
+
+
+        // test
+        ManagedIdentityCredential credential = new ManagedIdentityCredentialBuilder().clientId(CLIENT_ID).build();
+        StepVerifier.create(credential.getToken(request))
+            .expectErrorMatches(t -> t instanceof ClientAuthenticationException)
+            .verify();
+    }
+
 }