Identify Syntax & Logic Errors in Testing
Syntax errors and logic errors are thoroughly covered earlier in the course, you can find that revision note here
A summary of the two error types:
Syntax error: An error that breaks the grammatical rules of a programming language and stops it from running
Logic error: Incorrect code is used that allows the program to run, but produces an incorrect or undesired output
As a result of a syntax error breaking the rules of the programming language, the program will not execute
These are easily identifiable as the IDE will provide information about what the error is
This is done to help the programmer be able to fix the issue
To help practise this skill, a selection of program screenshots will be used
In the code below, there is a program which allows the user to enter how many items they wish to add to a shopping list
The code then allows the user to
Enter their chosen number of items into a list
Output the list to the screen
The code contains 3 syntax errors, highlighted with blue boxes
Line 3: Missing a second bracket at the end of integer input
The error message below is what the IDE provided to help the programmer identify the error
A top tip when programming is to look at the line of code above the one given in the error message
For example, this error message claims line 6 is the issue, however, the code above line 6 (line 3) is the line that contains the error
Line 6: Missing a colon at the end of a for loop, while loop or if statement
As mentioned earlier, the error message identifies the line after the actual error
The error is on line 6, however, the syntax error message identifies the line below it
Always check the line above for any potential errors
Line 7: Using == which is used for a comparison instead of a single = to declare a variable
This would return the same error as above, this time the user would more easily be able to identify the issue as it is on line 7
Once all fixes are in place, the code should appear as follows and the program should execute as intended
Logic errors can be slightly more challenging to locate compared to syntax errors
This is because the program will still run but will not produce the expected output that the programmer intended
The most obvious areas to check for logic errors are:
Logical operators (<, >, ==, !=)
Boolean operators (AND, OR, NOT)
Division by 0
To help demonstrate this skill, another snippet of program code is used
In this example, the incorrect Boolean operator has been used, OR instead of AND
The result means the else clause in the if statement would never be caught
At first glance, entering normal test data such as 14, the program works as intended
Entering erroneous data or boundary test data which is outside of the range would result in the error
When entering the age of 21, it still outputs that the user is in secondary school
By changing the OR to AND, this corrects the logic error
Dan is writing a program for maths students. To make sure that there are no logic errors in the program, Dan uses a test plan.
Describe what is meant by a logic error. [2]
Answer
The error does not prevent the program from running
But it does not produce the expected output / it does not do what the programmer intended
A reasonable example
Syntax errors and logic errors are thoroughly covered earlier in the course, you can find that revision note here
A summary of the two error types:
Syntax error: An error that breaks the grammatical rules of a programming language and stops it from running
Logic error: Incorrect code is used that allows the program to run, but produces an incorrect or undesired output
As a result of a syntax error breaking the rules of the programming language, the program will not execute
These are easily identifiable as the IDE will provide information about what the error is
This is done to help the programmer be able to fix the issue
To help practise this skill, a selection of program screenshots will be used
In the code below, there is a program which allows the user to enter how many items they wish to add to a shopping list
The code then allows the user to
Enter their chosen number of items into a list
Output the list to the screen
The code contains 3 syntax errors, highlighted with blue boxes
Line 3: Missing a second bracket at the end of integer input
The error message below is what the IDE provided to help the programmer identify the error
A top tip when programming is to look at the line of code above the one given in the error message
For example, this error message claims line 6 is the issue, however, the code above line 6 (line 3) is the line that contains the error
Line 6: Missing a colon at the end of a for loop, while loop or if statement
As mentioned earlier, the error message identifies the line after the actual error
The error is on line 6, however, the syntax error message identifies the line below it
Always check the line above for any potential errors
Line 7: Using == which is used for a comparison instead of a single = to declare a variable
This would return the same error as above, this time the user would more easily be able to identify the issue as it is on line 7
Once all fixes are in place, the code should appear as follows and the program should execute as intended
Logic errors can be slightly more challenging to locate compared to syntax errors
This is because the program will still run but will not produce the expected output that the programmer intended
The most obvious areas to check for logic errors are:
Logical operators (<, >, ==, !=)
Boolean operators (AND, OR, NOT)
Division by 0
To help demonstrate this skill, another snippet of program code is used
In this example, the incorrect Boolean operator has been used, OR instead of AND
The result means the else clause in the if statement would never be caught
At first glance, entering normal test data such as 14, the program works as intended
Entering erroneous data or boundary test data which is outside of the range would result in the error
When entering the age of 21, it still outputs that the user is in secondary school
By changing the OR to AND, this corrects the logic error
Dan is writing a program for maths students. To make sure that there are no logic errors in the program, Dan uses a test plan.
Describe what is meant by a logic error. [2]
Answer
The error does not prevent the program from running
But it does not produce the expected output / it does not do what the programmer intended
A reasonable example
