Fix error detection in nilm-sinefit, and improve test coverage for math.py

nilmtools/math.py

@@ -3,8 +3,18 @@
 # Miscellaenous useful mathematical functions
 from nilmdb.utils.printf import *
 from numpy import *
-from scipy import *
+import scipy
 
+def numpy_raise_errors(func):
+    def wrap(*args, **kwargs):
+        old = seterr('raise')
+        try:
+            return func(*args, **kwargs)
+        finally:
+            seterr(**old)
+    return wrap
+
+@numpy_raise_errors
 def sfit4(data, fs):
     """(A, f0, phi, C) = sfit4(data, fs)
 
@@ -25,10 +35,12 @@ def sfit4(data, fs):
     (Verified to match sfit4.m)
     """
     N = len(data)
+    if N < 2:
+        raise ValueError("bad data")
     t = linspace(0, (N-1) / float(fs), N)
 
     ## Estimate frequency using FFT (step b)
-    Fc = fft(data)
+    Fc = scipy.fft.fft(data)
     F = abs(Fc)
     F[0] = 0   # eliminate DC
 
@@ -76,7 +88,7 @@ def sfit4(data, fs):
         phi = arctan2(s[0], s[1]) # eqn B.22 (flipped for sin instead of cos)
         C = s[2]
         return (A, f0, phi, C)
-    except Exception as e:
+    except Exception as e: # pragma: no cover  (not sure if we can hit this?)
         # something broke down; just return zeros
         return (0, 0, 0, 0)
 

tests/test.py

@@ -763,7 +763,7 @@ class TestAllCommands(CommandTester):
         client.stream_create("/train/matches2", "uint8_1")
         self.ok(get_json("tests/data/trainola2.js"))
 
-    def test010_pipewatch(self):
+    def test_10_pipewatch(self):
         self.main = nilmtools.pipewatch.main
 
         self.fail(f"")
@@ -832,3 +832,9 @@ class TestAllCommands(CommandTester):
 
         self.ok(f"--yes tests/data/cleanup-nodecim.cfg")
         self.ok(f"--estimate tests/data/cleanup-nodecim.cfg")
+
+    def test_12_misc(self):
+        # Fill in test cases that were missed by earlier code
+        with assert_raises(ValueError):
+            nilmtools.math.sfit4([1], 5)
+        nilmtools.math.sfit4([1,2], 5)