Add signIn method test for SigninManagerTest

Add a test to check the signIn method in SigninManagerTest

Bug: 1059964
Change-Id: I953d4344fc50b892b793d6045aa7bf77d246141c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2095128Reviewed-by: Alice Wang <aliceywang@chromium.org>
Commit-Queue: Tanmoy Mollik <triploblastic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#751363}

chrome/android/junit/src/org/chromium/chrome/browser/signin/SigninManagerTest.java

@@ -10,6 +10,7 @@ import static org.junit.Assert.assertTrue;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.ArgumentMatchers.anyLong;
+import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.doNothing;
 import static org.mockito.Mockito.doReturn;
@@ -91,6 +92,20 @@ public class SigninManagerTest {
                 new CoreAccountId("gaia-id-user"), "user@domain.com", "gaia-id-user");
     }
 
+    @Test
+    public void signInFromJava() {
+        doReturn(true).when(mAccountTrackerService).checkAndSeedSystemAccounts();
+        doReturn(mAccount)
+                .when(mIdentityManager)
+                .findExtendedAccountInfoForAccountWithRefreshTokenByEmailAddress(
+                        eq(mAccount.getEmail()));
+
+        mSigninManager.onFirstRunCheckDone();
+        mSigninManager.signIn(SigninAccessPoint.START_PAGE, mAccount, null);
+
+        verify(mNativeMock).fetchAndApplyCloudPolicy(anyLong(), eq(mAccount), any());
+    }
+
     @Test
     public void signOutFromJavaWithManagedDomain() {
         // Stub out various native calls. Some of these are verified as never called