Add more unit test coverage for GetUserName

tests/test-getusername.cpp

@@ -14,31 +14,108 @@ protected:
 
 	GetUserNameTest(): userName(std::string(getlogin())) {}
 
-	void GetUserNameWithSize(DWORD size) {
+	void TestWithSize(DWORD size) {
 		lpnSize = size;
 		// allocate a WCHAR_T buffer to receive username
 		lpBuffer.assign(lpnSize, '\0');
 		result = GetUserName(&lpBuffer[0], &lpnSize);
 	}
+
+	void TestSuccess() {
+		SCOPED_TRACE("");
+		// returns 1 on success
+		EXPECT_EQ(1, result);
+
+		// sets lpnSize to length of username + null
+		ASSERT_EQ(userName.size()+1, lpnSize);
+
+		// copy UTF-16 bytes (excluding null) from lpBuffer to vector for conversion
+		unsigned char *begin = reinterpret_cast<unsigned char *>(&lpBuffer[0]);
+		// -1 to skip null; *2 because UTF-16 encodes two bytes per character
+		unsigned char *end = begin + (lpnSize-1)*2;
+		std::vector<unsigned char> input(begin, end);
+		// convert to UTF-8 for comparison
+		std::string output;
+		SCXCoreLib::Utf16leToUtf8(input, output);
+
+		EXPECT_EQ(userName, output);
+	}
+
+	void TestInvalidParameter() {
+		SCOPED_TRACE("");
+
+		// returns 0 on failure
+		EXPECT_EQ(0, result);
+
+		// sets errno to ERROR_INVALID_PARAMETER when lpBuffer is null
+		// (which is the case for an empty vector)
+		EXPECT_EQ(errno, ERROR_INVALID_PARAMETER);
+	}
+
+	void TestInsufficientBuffer() {
+		SCOPED_TRACE("");
+
+		// returns 0 on failure
+		EXPECT_EQ(0, result);
+
+		// sets errno to ERROR_INSUFFICIENT_BUFFER
+		EXPECT_EQ(errno, ERROR_INSUFFICIENT_BUFFER);
+
+		// sets lpnSize to length of username + null
+		EXPECT_EQ(userName.size()+1, lpnSize);
+	}
 };
 
-TEST_F(GetUserNameTest, NormalUse) {
-	GetUserNameWithSize(L_cuserid);
+TEST_F(GetUserNameTest, BufferAsNullButNotBufferSize) {
+	lpnSize = 1;
+	result = GetUserName(NULL, &lpnSize);
 
-	// GetUserName returns 1 on success
-	ASSERT_EQ(1, result);
-
-	// GetUserName sets lpnSize to length of username including null
-	ASSERT_EQ(userName.size()+1, lpnSize);
-
-	// copy UTF-16 bytes (excluding null) from lpBuffer to vector for conversion
-	unsigned char *begin = reinterpret_cast<unsigned char *>(&lpBuffer[0]);
-	// -1 to skip null; *2 because UTF-16 encodes two bytes per character
-	unsigned char *end = begin + (lpnSize-1)*2;
-	std::vector<unsigned char> input(begin, end);
-	// convert to UTF-8 for assertion
-	std::string output;
-	SCXCoreLib::Utf16leToUtf8(input, output);
-
-	EXPECT_EQ(userName, output);
+	TestInvalidParameter();
+	// does not reset lpnSize
+	EXPECT_EQ(1, lpnSize);
+}
+
+TEST_F(GetUserNameTest, BufferSizeAsNullButNotBuffer) {
+	lpBuffer.push_back('\0');
+	result = GetUserName(&lpBuffer[0], NULL);
+
+	TestInvalidParameter();
+}
+
+TEST_F(GetUserNameTest, BufferSizeAsZero) {
+	TestWithSize(0);
+	TestInvalidParameter();
+	// does not reset lpnSize
+	EXPECT_EQ(0, lpnSize);
+}
+
+TEST_F(GetUserNameTest, BufferSizeAsOne) {
+	// theoretically this should never fail because any non-empty
+	// username length will be >1 with trailing null
+	TestWithSize(1);
+	TestInsufficientBuffer();
+}
+
+TEST_F(GetUserNameTest, BufferSizeAsUserName) {
+	// the buffer is too small because this does not include null
+	TestWithSize(userName.size());
+	TestInsufficientBuffer();
+}
+
+TEST_F(GetUserNameTest, BufferSizeAsUserNameMinusOne) {
+	// the buffer is also too small
+	TestWithSize(userName.size()-1);
+	TestInsufficientBuffer();
+}
+
+TEST_F(GetUserNameTest, BufferSizeAsUserNamePlusOne) {
+	// the buffer is exactly big enough will null
+	TestWithSize(userName.size()+1);
+	TestSuccess();
+}
+
+TEST_F(GetUserNameTest, L_cuseridSize) {
+	// L_cuserid is big enough to hold any username
+	TestWithSize(L_cuserid);
+	TestSuccess();
 }