Add unit tests for Times.c

[dschlaep]

High priority functions for which to write unit tests:

• interpolate_monthlyValues

[nip5]

@dschlaep Can I changed the return value in interpolate_monthlyValues from void in order to return the interpolated daily values? This is the only way this is testable since as it stands now there are no pointer arguments either. Also the comments above the function say that the daily values are the output.

[dschlaep]

I really don't see the problem and thus I don't see the need to change return from a cheap void to an expensive copy of dailyValues. The output values are returned in dailyValues.

Look for instance at how this function is used in SW_SKY_init:

interpolate_monthlyValues(v->cloudcov, v->cloudcov_daily);

where inputs = v->cloudcov and outputs v->cloudcov_daily.

[nip5]

I'm not certain that that would actually update v -> cloudcov_daily since the second argument isn't a pointer so all changes to that member variable would be just locally in the function. Is there any proof in the code that this works? I ran some tests in the SOILWAT code directly after it is called (when it should have updated) and the value of cloudcov_daily does not update after the call
interpolate_monthlyValues(v->cloudcov, v->cloudcov_daily);

[dschlaep]

Well, the second argument is an array, thus it decays into a pointer to the first array element when passed as argument to a function; the works just fine. Read up on your c (e.g., http://c-faq.com/aryptr/aryptrparam.html).

However, what you see when you only look at the first array element is a bug in the function, i.e., that it returns 0 for the first day.

swprintf("'SW_SKY_init' before: " \
  "cc_monthly[Jan] = %f, cc_monthly[Feb] = %f, \n" \
  "\tcc_daily[Jan 1] = %f, cc_daily[Jan 15] = %f, cc_daily[Feb 1] = %f\n",
  v->cloudcov[0], v->cloudcov[1],
  v->cloudcov_daily[0], v->cloudcov_daily[14], v->cloudcov_daily[31]);

	interpolate_monthlyValues(v->cloudcov, v->cloudcov_daily);

swprintf("'SW_SKY_init' after: " \
  "cc_monthly[Jan] = %f, cc_monthly[Feb] = %f, \n" \
  "\tcc_daily[Jan 1] = %f, cc_daily[Jan 2] = %f, cc_daily[Jan 14] = %f, cc_daily[Jan 15] = %f, cc_daily[Feb 1] = %f\n",
  v->cloudcov[0], v->cloudcov[1],
  v->cloudcov_daily[0], v->cloudcov_daily[1], v->cloudcov_daily[13], v->cloudcov_daily[14], v->cloudcov_daily[31]);

'SW_SKY_init' before: cc_monthly[Jan] = 71.000000, cc_monthly[Feb] = 61.000000, 
	cc_daily[Jan 1] = 0.000000, cc_daily[Jan 15] = 0.000000, cc_daily[Feb 1] = 0.000000
'SW_SKY_init' after: cc_monthly[Jan] = 71.000000, cc_monthly[Feb] = 61.000000, 
	cc_daily[Jan 1] = 0.000000, cc_daily[Jan 2] = 66.483871, cc_daily[Jan 14] = 70.354839, cc_daily[Jan 15] = 70.677419, cc_daily[Feb 1] = 65.838710

[dschlaep]

@nip5 @CaitlinA Would you please open an issue dedicated document this bug at index 0? This seems to be a base0--base1 problem. And ideally write a test that fails, and then fix it? Thanks.