RemoveStringFromCSV: add unit test

Tested: only added a unit test and it passed.

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Change-Id: If68e47545f184b9fa22d701e78fb15b2b1b7949f
diff --git a/test/user_mgr_test.cpp b/test/user_mgr_test.cpp
index 22a8837..ee45482 100644
--- a/test/user_mgr_test.cpp
+++ b/test/user_mgr_test.cpp
@@ -160,5 +160,28 @@
               "123,456");
 }
 
+TEST(RemoveStringFromCSV, WithoutDeleteStringReturnsFalse)
+{
+    std::string expected = "whatever,https";
+    std::string str = expected;
+    EXPECT_FALSE(removeStringFromCSV(str, "ssh"));
+    EXPECT_EQ(str, expected);
+
+    std::string empty;
+    EXPECT_FALSE(removeStringFromCSV(empty, "ssh"));
+}
+
+TEST(RemoveStringFromCSV, WithDeleteStringReturnsTrue)
+{
+    std::string expected = "whatever";
+    std::string str = "whatever,https";
+    EXPECT_TRUE(removeStringFromCSV(str, "https"));
+    EXPECT_EQ(str, expected);
+
+    str = "https";
+    EXPECT_TRUE(removeStringFromCSV(str, "https"));
+    EXPECT_EQ(str, "");
+}
+
 } // namespace user
 } // namespace phosphor