sympy/sympy — pull request #1620 by jrioux (2012-10-29 15:18:37+00:00)
Title: integrate(DiracDelta(y - x), x)

Fix an simple DiracDelta integral, reorganize tests and add some tests.

Before:
```
>>> integrate(DiracDelta(y - x), x)
Heaviside(y - x)
>>> integrate(DiracDelta(y - x), (x, -oo, oo))
-1
```

After:
```
>>> integrate(DiracDelta(y - x), x)
Heaviside(x - y)
>>> integrate(DiracDelta(y - x), (x, -oo, oo))
1
```