### Question:
SystemVariableCredentialsProvider implements CredentialsProvider { @Override public Credentials getCredentials() { return credentials; } SystemVariableCredentialsProvider();  SystemVariableCredentialsProvider(String usernameKey, String passwordKey); @Override Credentials getCredentials(); @Override CredentialsProvider refresh();  }### Answer:
@Test public void testConstructorWithParams() { CredentialsProvider provider = new SystemVariableCredentialsProvider(userNameSysProp, userPasswordSysProp); Credentials credentials = provider.getCredentials(); assert userName.equals(credentials.getUsername()); assert userPassword.equals(credentials.getPassword()); }
@Test public void testDefaultConstructor() { CredentialsProvider provider = new SystemVariableCredentialsProvider(userNameSysProp, userPasswordSysProp); assert provider.getCredentials().isEqualTo(new Credentials(userName, userPassword)); }