add unittests for mc01td, fix dp constraint

slycot/src/math.pyf

@@ -3,7 +3,7 @@
 
 subroutine mc01td(dico,dp,p,stable,nz,dwork,iwarn,info) ! in :new:MC01TD.f
 	character :: dico
-	integer intent(in,out),check(dp>0) :: dp
+	integer intent(in,out),check(dp>=0) :: dp
 	double precision intent(in),check(shape(p,0)==dp+1),dimension(dp+1),depend(dp) :: p
 	logical intent(out) :: stable
 	integer intent(out) :: nz

slycot/tests/test_mc.py

@@ -0,0 +1,46 @@
+#!/usr/bin/env python
+#
+# test_mc.py - test suite for polynomial and rational function manipulation
+# bnavigator <code@bnavigator.de>, Aug 2019
+
+import unittest
+import warnings
+
+from slycot import mc01td
+
+
+class test_mc(unittest.TestCase):
+
+    def test_mc01td(self):
+        """ test_mc01td: doc example
+        data from http://slicot.org/objects/software/shared/doc/MC01TD.html
+        """
+        (dp, stable, nz) = mc01td('C', 4, [2, 0, 1, -1, 1])
+        self.assertEqual(dp, 4)
+        self.assertEqual(stable, 0)
+        self.assertEqual(nz, 2)
+
+    def test_mc01td_D(self):
+        """ test_mc01td_D: test discrete option """
+        (dp, stable, nz) = mc01td('D', 3, [1, 2, 3, 4])
+        self.assertEqual(dp, 2)
+        self.assertEqual(stable, 1)
+        self.assertEqual(nz, 0)
+        (dp, stable, nz) = mc01td('D', 3, [4, 3, 2, 1])
+        self.assertEqual(dp, 3)
+        self.assertEqual(stable, 0)
+        self.assertEqual(nz, 3)
+
+    def test_mc01td_warnings(self):
+        """ test_mc01td_warnings: Test warnings """
+        T = [([0, 0], "entry P(x) is the zero polynomial."),
+             ([0, 1], "P(x) may have zeros very close to stability boundary."),
+             ([1, 0], "The degree of P(x) has been reduced to 0")]
+        for P, m in T:
+            with warnings.catch_warnings(record=True) as w:
+                (dp, stable, nz) = mc01td('C', len(P)-1, P)
+                self.assertEqual(w[0].message, m)
+
+
+if __name__ == "__main__":
+    unittest.main()