Unit Testing in IDL
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Unit Testing in IDL
Anonym Thursday, May 7, 2015
One of the key aspects of developing any software is testing. Making sure the software behaves as you expect for a variety of inputs is crucial for creating robust and maintainable code. Testing in IDL can be a little tricky and will often require you implement your own system for maintaining tests. However, with a little framework this task can be a lot less daunting.
Before we get into the framework, it would be beneficial to read up on Test Driven Development and the concepts behind writing good tests. There are some great tutorials and overviews on the web and they really help to emphasize the importance of testing. Now, onto the code!
Let’s say we want to write a function CONVERT_TO_STRING. Since we are writing this function from scratch, let’s define the contract of the function. As input, it will take an IDL variable, convert it to a string with a custom format, and return it. Great, let’s write some tests
test_convert_to_string.pro:
pro test_convert_to_string_number
compile_opt idl2
on_error, 2
input = 1
expect = '1'
result = convert_to_string(input)
if result ne expect then begin
message, 'Converting number failed.'
endif
end
pro test_convert_to_string_null
compile_opt idl2
on_error, 2
input = !NULL
expect = '!NULL'
result = convert_to_string(input)
if result ne expect then begin
message, 'Converting number failed.'
endif
end
pro test_convert_to_string_object
compile_opt idl2
on_error, 2
input = hash('a',1,'b',2,'c',3)
expect = '{"c":3,"a":1,"b":2}'
result = convert_to_string(input)
if result ne expect then begin
message, 'Converting number failed.'
endif
end
pro test_convert_to_string
compile_opt idl2
print, 'Testing suite for convert_to_string()'
end
Before any code is written we have our test case. The reason we can do this is because we defined the contract of the function. We know exactly what the function should take in as input and what the output should be. Now running this code can be a little tiresome to run so let’s setup some framework.
unit_test_runner.pro:
; Path – path to test directory
pro unit_test_runner, path
compile_opt idl2
if ~file_test(path, /directory) then begin
message, 'Input must be a path.'
endif
test_files = file_search(path, 'test*.pro')
resolve_routine, file_basename(test_files,'.pro'), /compile_full_file
tests = routine_info()
print,'--------------------------------------------------------------------------------'
error_count = 0
for i=0, tests.length-1 do begin
catch, errorStatus
if (errorStatus ne 0) then begin
catch, /cancel
print, 'ERROR: ', !ERROR_STATE.msg
i++
error_count++
continue
endif
if (tests[i]).startswith('TEST_') then begin
call_procedure, tests[i]
endif
endfor
print,'--------------------------------------------------------------------------------'
if error_count gt 0 then begin
print, 'Unit test failures on: ' + path
endif else begin
print, 'Unit tests pass.'
endelse
end
Now all we have to do is give UNIT_TEST_RUNNER a path to our test files and it will run them! Let’s get busy coding.
convert_to_string.pro:
; Input - IDL Variable
; Output - Custom string representation of the variable
function convert_to_string, var
compile_opt idl2
switch size(var,/TYPE) of
0: begin
return, '!NULL '
break
end
11: begin
if isa(var,'HASH') or isa(var,'DICTIONARY') or isa(var,'ORDEREDHASH') then begin
return, json_serialize(var)
endif
break
end
else: begin
return, strtrim(var,2)
end
endswitch
end
Now let’s run our test suite:
Testing suite for convert_to_string()
% Compiled module: CONVERT_TO_STRING.
ERROR: TEST_CONVERT_TO_STRING_NULL: Converting !NULL failed.
Unit test failures on: C:\convert_to_string
Oops! Our return for the !NULL case isn’t what we are expecting (good thing it’s an easy fix).
By developing software test first you are forced to think about the contract (inputs/outputs) of each function. By implementing unit tests against this contract, we can then use our new function with confidence. If everything has unit tests any problems which arise in the code are easily identified and fixed.
Note: Make sure each code segment is saved to a named file (names are given before the code) and all files are on your IDL PATH.
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