Add the test test_connect_unique_connection_neuron_0_to_neuron_0. It tests if only neuron 0 of population 1 is connected to neuron 0 of population 2. The test fails on the current master branch, and the bug is resolved in the pull request unittests for hardware backends, from the branch JoelChavas:test_brainscales_backend
Adding test test_connect_weight_function_and_one_post_synaptic_neuron_not_connected. This test guarantees that we can have a postsynaptic neuron not connected. This test is to correct for a bug introduced in the commit 5335d428, more precisely to test against this bug.
Correction over MockRNG3 that should give integers as presynaptic indices