Experiment.set_phase(): normalize negative phases to [0, 360)

The phase was passed to the backend job file verbatim, so negative
values (e.g. from rf_pulse(phase=-90)) reached the backend unchanged.
set_phase(), set_frequency() and thus rf_pulse() now write the phase
normalized with phase % 360. Add unittests for the normalization.

tests/test_Experiment.py

@@ -0,0 +1,47 @@
+import re
+import unittest
+
+from damaris.experiments.Experiment import Experiment
+
+
+def phase_of_state(state):
+    "extracts the phase value from a state's XML content"
+    match = re.search(r'phase="([-0-9.]+)"', state.content)
+    assert match, "no phase in state: %s" % state.content
+    return float(match.group(1))
+
+
+class TestExperimentPhase(unittest.TestCase):
+    def test_set_phase_negative_normalized(self):
+        """Test that set_phase() normalizes negative phases to [0, 360)."""
+        e = Experiment()
+        for degrees, expected in ((-90, 270.0), (-45.5, 314.5),
+                                  (-270, 90.0), (-360, 0.0)):
+            e.set_phase(degrees)
+            self.assertEqual(phase_of_state(e.state_list.list[-1]), expected)
+
+    def test_set_phase_positive_unchanged(self):
+        """Test that set_phase() passes positive phases through unchanged."""
+        e = Experiment()
+        for degrees, expected in ((0, 0.0), (90, 90.0), (270, 270.0),
+                                  (45.5, 45.5)):
+            e.set_phase(degrees)
+            self.assertEqual(phase_of_state(e.state_list.list[-1]), expected)
+
+    def test_set_frequency_negative_phase_normalized(self):
+        """Test that set_frequency() normalizes a negative phase."""
+        e = Experiment()
+        e.set_frequency(85e6, -90)
+        state = e.state_list.list[-1]
+        self.assertEqual(phase_of_state(state), 270.0)
+        self.assertIn('f="85000000.000000"', state.content)
+
+    def test_rf_pulse_negative_phase_normalized(self):
+        """Test that rf_pulse() normalizes a negative pulse phase."""
+        e = Experiment(gating=1e-6, rf_sources=[1], rf_gates=[2])
+        e.rf_pulse(length=1e-6, phase=-90, source=0)
+        self.assertEqual(phase_of_state(e.state_list.list[0]), 270.0)
+
+
+if __name__ == "__main__":
+    unittest.main()