Pytest enhancements

Adds

1. A pytest marker generate that marks a test as generating test data. These tests will only be run when the --generate flag is given, and all other tests won't be run in this case. This prevents accidentally overwriting test data.
2. A pytest fixture compare_noise which checks whether all noises in a budget are the same as in another budget. A list of noises passing, failing, or skipped is printed and an assertion error is raised if any traces are different.

The unit tests test_save_budgets and test_check_noise are added to test/budgets/test_budgets.py making use of the new fixture and marker. The compare_noise fixture is useful because it quickly checks if noises are the same and fails if any are different. So you can have pytest both continuously plotting a budget and quickly checking if any noises have changed by doing for example

ptw -- test/budgets/test_budgets.py -s -k test_check_noise
ptw -- test/budgets/test_budgets.py -s -k test_load[Aplus]

conftest.py

@@ -296,21 +296,27 @@ def compare_noise(pprint):
         passed = []
         failed = []
         skipped = []
-        for ref_trace in ref_traces:
-            if np.all(ref_trace.psd < psd_tol):
-                skipped.append(ref_trace.name)
-                continue
-
-            try:
-                trace = traces[ref_trace.name]
-            except KeyError:
-                skipped.append(ref_trace.name)
-                continue
-
-            if np.allclose(trace.psd, ref_trace.psd, atol=0):
-                passed.append(trace.name)
+        if ref_traces.budget:
+            for ref_trace in ref_traces:
+                if np.all(ref_trace.psd < psd_tol):
+                    skipped.append(ref_trace.name)
+                    continue
+
+                try:
+                    trace = traces[ref_trace.name]
+                except KeyError:
+                    skipped.append(ref_trace.name)
+                    continue
+
+                if np.allclose(trace.psd, ref_trace.psd, atol=0):
+                    passed.append(trace.name)
+                else:
+                    failed.append(trace.name)
+        else:
+            if np.allclose(ref_traces.psd, traces.psd, atol=0):
+                passed.append(traces.name)
             else:
-                failed.append(trace.name)
+                failed.append(traces.name)
 
         pprint('Noises failed:')
         pprint(40 * '-')