Add tests for differential operators

This should hopefully improve coverage.

One of these tests fails right now

Author: eric-wieser

test/test_differential_ops.py

@@ -0,0 +1,83 @@
+from sympy import symbols
+import pytest
+
+from galgebra.ga import Ga
+from galgebra.mv import Dop
+
+
+class TestDop(object):
+
+    def test_associativity_and_distributivity(self):
+        coords = x, y, z = symbols('x y z', real=True)
+        ga, ex, ey, ez = Ga.build('e*x|y|z', g=[1, 1, 1], coords=coords)
+        v = ga.mv('v', 'vector', f=True)
+        laplacian = ga.grad * ga.grad
+        rlaplacian = ga.rgrad * ga.rgrad
+
+        # check addition distributes
+        assert (laplacian + ga.grad) * v == laplacian * v + ga.grad * v != 0
+        assert (laplacian + 1234567) * v == laplacian * v + 1234567 * v != 0
+        # check subtraction distributes
+        assert (laplacian - ga.grad) * v == laplacian * v - ga.grad * v != 0
+        assert (laplacian - 1234567) * v == laplacian * v - 1234567 * v != 0
+        # check unary subtraction distributes
+        assert (-ga.grad) * v == -(ga.grad * v) != 0
+        # check division is associative
+        assert v * (ga.rgrad / 2) == (v * ga.rgrad) / 2 != 0
+        # check multiplication is associative
+        assert (20 * ga.grad) * v == 20 * (ga.grad * v) != 0
+        assert v * (ga.rgrad * 20) == (v * ga.rgrad) * 20 != 0
+        assert (ex ^ ga.grad) ^ v == ex ^ (ga.grad ^ v) != 0
+        assert (20 ^ ga.grad) ^ v == 20 ^ (ga.grad ^ v) != 0
+        assert v ^ (ga.rgrad ^ ex) == (v ^ ga.rgrad) ^ ex != 0
+        assert v ^ (ga.rgrad ^ 20) == (v ^ ga.rgrad) ^ 20 != 0
+
+    @pytest.mark.xfail(raises=IndexError)
+    def test_empty_dop(self):
+        """ Test that dop with zero terms is equivalent to multiplying by zero """
+        coords = x, y, z = symbols('x y z', real=True)
+        ga, ex, ey, ez = Ga.build('e*x|y|z', g=[1, 1, 1], coords=coords)
+        v = ga.mv('v', 'vector', f=True)
+
+        make_zero = Dop([], ga=ga)
+        assert make_zero * v == 0
+        assert make_zero * make_zero * v == 0
+        assert (make_zero + make_zero) * v == 0
+        assert (-make_zero) * v == 0
+
+    def test_misc(self):
+        """ Other miscellaneous tests """
+        coords = x, y, z = symbols('x y z', real=True)
+        ga, ex, ey, ez = Ga.build('e*x|y|z', g=[1, 1, 1], coords=coords)
+        v = ga.mv('v', 'vector', f=True)
+        laplacian = ga.grad * ga.grad
+        rlaplacian = ga.rgrad * ga.rgrad
+
+        # laplacian is a scalar operator, so applying it from either side
+        # is the same
+        assert laplacian * v == v * rlaplacian
+
+        assert laplacian.is_scalar()
+        assert not ga.grad.is_scalar()
+
+        # inconsistent cmpflg, not clear which side the operator goes on
+        with pytest.raises(ValueError):
+            ga.grad + ga.rgrad
+        with pytest.raises(ValueError):
+            ga.grad * ga.rgrad
+
+    def test_mixed_algebras(self):
+        coords = x, y, z = symbols('x y z', real=True)
+        ga1, ex1, ey1, ez1 = Ga.build('e1*x|y|z', g=[1, 1, 1], coords=coords)
+        ga2, ex2, ey2, ez2 = Ga.build('e2*x|y|z', g=[1, 1, 1], coords=coords)
+        assert ga1 != ga2
+
+        v1 = ga1.mv('v', 'vector', f=True)
+        v2 = ga2.mv('v', 'vector', f=True)
+
+        with pytest.raises(ValueError):
+            ga1.grad * v2
+        with pytest.raises(ValueError):
+            v1 * ga2.rgrad
+        with pytest.raises(ValueError):
+            ga1.grad * ga2.grad