Hands-On Dependency Injection in Go

Testing error handling

There are three possible errors we need to handle:

• The SQL insert could fail
• Failure to get the database
• We could fail to retrieve the ID of the inserted record

So, how do we test for SQL insert failure? With SQLMock it's easy: we make a copy of the previous test and instead of returning sql.Result, we return an error, as shown in the following code:

// configure the mock dbqueryRegex := convertSQLToRegex(sqlInsert)dbMock.ExpectExec(queryRegex).WillReturnError(errors.New("failed to insert"))

We can then change our expectations from a result to an error, as shown in the following code:

require.Error(t, err)assert.Equal(t, defaultPersonID, resultID)assert.NoError(t, dbMock.ExpectationsWereMet())

Moving on to testing ...