Have proper test skipping

Also clear cache in sympy in tests. Only memory leak left is
because of the cyclic reference in PySymbol

Author: isuruf

symengine/lib/symengine_wrapper.pyx

@@ -376,7 +376,15 @@ def _sympify(a, raise_error=True):
         return _sympify(a._sympy_(), raise_error)
     elif hasattr(a, 'pyobject'):
         return _sympify(a.pyobject(), raise_error)
-    return sympy2symengine(a, raise_error)
+
+    try:
+        import sympy
+        return sympy2symengine(a, raise_error)
+    except ImportError:
+        pass
+
+    if raise_error:
+        raise SympifyError("sympify: Cannot convert '%r' to a symengine type." % a)
 
 funcs = {}
 

symengine/tests/test_eval.py

@@ -2,7 +2,7 @@
 from symengine import (Symbol, sin, cos, Integer, Add, I, RealDouble, ComplexDouble, sqrt)
 
 from symengine.lib.symengine_wrapper import eval_double
-
+from unittest.case import SkipTest
 
 def test_eval_double1():
     x = Symbol("x")
@@ -34,6 +34,8 @@ def test_n():
     y = 1.0 + 2.0*I
     assert x.n() == y
 
+
+def test_n_mpfr():
     try:
         from symengine import RealMPFR
         x = sqrt(Integer(2))
@@ -42,7 +44,10 @@ def test_n():
     except ImportError:
         x = sqrt(Integer(2))
         raises(ValueError, lambda: (x.n(75, real=True)))
+        raise SkipTest("No MPFR support")
+
 
+def test_n_mpc():
     try:
         from symengine import ComplexMPC
         x = sqrt(Integer(2)) + 3*I
@@ -51,6 +56,7 @@ def test_n():
     except ImportError:
         x = sqrt(Integer(2))
         raises(ValueError, lambda: (x.n(75)))
+        raise SkipTest("No MPC support")
 
 
 def test_rel():

symengine/tests/test_functions.py

@@ -1,6 +1,15 @@
 from symengine import Symbol, sin, cos, sqrt, Add, Mul, function_symbol, Integer, log, E, symbols
 from symengine.lib.symengine_wrapper import Subs, Derivative
+import unittest
 
+try:
+    import sympy
+    from sympy.core.cache import clear_cache
+    import atexit
+    atexit.register(clear_cache)
+    have_sympy = True
+except ImportError:
+    have_sympy = False
 
 def test_sin():
     x = Symbol("x")
@@ -105,6 +114,7 @@ def test_Subs():
     assert s.point == (2*x,)
 
 
+@unittest.skipUnless(have_sympy, "SymPy not installed")
 def test_FunctionWrapper():
     import sympy
     n, m, theta, phi = sympy.symbols("n, m, theta, phi")