Resolve "Testing issue: py-cerebrus"

Closes #28 (closed)

packages/py-cerebrus/package.py

@@ -17,4 +17,5 @@ class PyCerebrus(PythonPackage):
     version('1.3.4', sha256='d1b21b3954b2498d9a79edf16b3170a3ac1021df88d197dc2ce5928ba519237c')
 
     depends_on('python@3.6.9:')
-    depends_on('py-setuptools',     type=('build', 'run'))
\ No newline at end of file
+    depends_on('py-setuptools',     type=('build', 'run'))
+    depends_on('py-pytest',         type=('test'))