Add tests for coil_current

- Adds new parameters into the test framework

qcodes/instrument/sims/AMI430.yaml

@@ -103,6 +103,15 @@ devices:
           q: "RAMP"
           r: OK
 
+      current rating:
+        default: 3
+        getter:
+          q: "CURR:RATING?"
+          r: "{}"
+        setter:
+          q: "CONF:CURR:RATING {}"
+          r: OK
+
 
 resources:  # we always need three power supplies; one for each axis. For the testing we add a few more
   GPIB::1::INSTR:

qcodes/instrument_drivers/american_magnetics/AMI430.py

@@ -138,17 +138,19 @@ def __init__(self, name, address=None, port=None,
                                          'tesla': 1})
 
         # Set programatic safety limits
-        if current_ramp_limit is None:
-            self._update_ramp_rate_limit(AMI430._DEFAULT_CURRENT_RAMP_LIMIT, update=False)
-        else:
-            self._update_ramp_rate_limit(current_ramp_limit, update=False)
         self.add_parameter('current_ramp_limit',
                             get_cmd=lambda: self._current_ramp_limit,
-                            set_cmd=self._update_ramp_rate_limit)
+                            set_cmd=self._update_ramp_rate_limit,
+                            unit="A/s")
         self.add_parameter('field_ramp_limit',
                             get_cmd=lambda: self.current_ramp_limit(),
                             set_cmd=lambda x: self.current_ramp_limit(x),
-                            scale=1/float(self.ask("COIL?")))
+                            scale=1/float(self.ask("COIL?")),
+                            unit="T/s")
+        if current_ramp_limit is None:
+            self._update_ramp_rate_limit(AMI430._DEFAULT_CURRENT_RAMP_LIMIT, update=False)
+        else:
+            self._update_ramp_rate_limit(current_ramp_limit, update=False)
 
         # Add solenoid parameters
         self.add_parameter('coil_constant',

qcodes/tests/drivers/test_ami430.py

@@ -385,31 +385,32 @@ def test_warning_increased_max_ramp_rate():
     ramp rate. We want the user to be really sure what he or she is
     doing, as this could risk quenching the magnet
     """
-    max_ramp_rate = AMI430_VISA.default_current_ramp_limit
+    max_ramp_rate = AMI430_VISA._DEFAULT_CURRENT_RAMP_LIMIT
     # Increasing the maximum ramp rate should raise a warning
     target_ramp_rate = max_ramp_rate + 0.01
 
-    with pytest.raises(Warning) as excinfo:
+    with pytest.warns(Warning) as excinfo:
         AMI430_VISA("testing_increased_max_ramp_rate",
                     address='GPIB::4::65535::INSTR', visalib=visalib,
                     terminator='\n', port=1,
                     current_ramp_limit=target_ramp_rate)
 
-    assert "Increasing maximum ramp rate" in excinfo.value.args[0]
+        assert len(excinfo) == 1 # Check we onlt saw one warning
+        assert "Increasing maximum ramp rate" in excinfo[0].message.args[0]
 
 
 def test_ramp_rate_exception(current_driver):
     """
     Test that an exception is raised if we try to set the ramp rate
     to a higher value than is allowed
     """
-    max_ramp_rate = AMI430_VISA.default_current_ramp_limit
+    max_ramp_rate = AMI430_VISA._DEFAULT_CURRENT_RAMP_LIMIT
     target_ramp_rate = max_ramp_rate + 0.01
     ix = current_driver._instrument_x
 
     with pytest.raises(Exception) as excinfo:
         ix.ramp_rate(target_ramp_rate)
 
-    errmsg = "must be between 0 and {} inclusive".format(max_ramp_rate)
+        errmsg = "must be between 0 and {} inclusive".format(max_ramp_rate)
 
-    assert errmsg in excinfo.value.args[0]
+        assert errmsg in excinfo.value.args[0]