diff --git a/brian2modelfitting/fitter.py b/brian2modelfitting/fitter.py
index fe66bbd5..76d13164 100644
--- a/brian2modelfitting/fitter.py
+++ b/brian2modelfitting/fitter.py
@@ -850,7 +850,7 @@ def _callback_wrapper(params, iter, resid, *args, **kwds):
 class SpikeFitter(Fitter):
     def __init__(self, model, input, output, dt, reset, threshold,
                  input_var='I', refractory=False, n_samples=30,
-                 method=None, level=0, param_init=None):
+                 method=None, param_init=None):
         """Initialize the fitter."""
         if method is None:
             method = 'exponential_euler'
diff --git a/brian2modelfitting/tests/test_modelfitting_spikefitter.py b/brian2modelfitting/tests/test_modelfitting_spikefitter.py
index 68538c09..dc3a6ca5 100644
--- a/brian2modelfitting/tests/test_modelfitting_spikefitter.py
+++ b/brian2modelfitting/tests/test_modelfitting_spikefitter.py
@@ -7,7 +7,7 @@
 from brian2 import (Equations, NeuronGroup, SpikeMonitor, TimedArray,
                     nS, nF, mV, ms, nA, amp, run)
 from brian2modelfitting import (NevergradOptimizer, SpikeFitter, GammaFactor,
-                                Simulator, Metric, Optimizer)
+                                Simulator, Metric, Optimizer, MSEMetric)
 from brian2modelfitting.fitter import get_spikes
 from brian2.devices.device import reinit_devices
 
@@ -101,14 +101,22 @@ def test_spikefitter_init(setup):
     assert isinstance(sf.model, Equations)
 
 
-def test_tracefitter_init_errors(setup):
+def test_spikefitter_init_errors(setup):
     dt, _ = setup
     with pytest.raises(Exception):
         SpikeFitter(model=model, input_var='Exception', dt=dt,
                     input=inp_trace*amp, output=output,
                     n_samples=2,
                     threshold='v > -50*mV',
-                    reset='v = -70*mV',)
+                    reset='v = -70*mV')
+
+    with pytest.raises(ValueError):
+        sf = SpikeFitter(model=model, input_var='I', dt=dt,
+                         input=inp_trace * amp, output=output,
+                         n_samples=2,
+                         threshold='v > -50*mV',
+                         reset='v = -70*mV',
+                         param_init={'V': -70*mV})  # name is "v" not "V"
 
 
 def test_spikefitter_fit(setup):
@@ -134,6 +142,23 @@ def test_spikefitter_fit(setup):
     assert_equal(results, sf.best_params)
 
 
+def test_spikefitter_fit_errors(setup):
+    dt, sf = setup
+    with pytest.raises(TypeError):
+        results, errors = sf.fit(n_rounds=2,
+                                 optimizer=n_opt,
+                                 metric=MSEMetric(),
+                                 gL=[20*nS, 40*nS],
+                                 C=[0.5*nF, 1.5*nF])
+    with pytest.raises(TypeError):
+        results, errors = sf.fit(n_rounds=2,
+                                 optimizer=None,
+                                 metric=MSEMetric(),
+                                 gL=[20*nS, 40*nS],
+                                 C=[0.5*nF, 1.5*nF])
+
+
+
 def test_spikefitter_param_init(setup):
     dt, _ = setup
     SpikeFitter(model=model, input_var='I', dt=dt,
diff --git a/brian2modelfitting/tests/test_modelfitting_tracefitter.py b/brian2modelfitting/tests/test_modelfitting_tracefitter.py
index 16f32d9d..9a3f07c5 100644
--- a/brian2modelfitting/tests/test_modelfitting_tracefitter.py
+++ b/brian2modelfitting/tests/test_modelfitting_tracefitter.py
@@ -208,6 +208,44 @@ def test_fitter_fit(setup):
     assert_equal(results, tf.best_params)
 
 
+def test_fitter_fit_callback(setup):
+    dt, tf = setup
+
+    calls = []
+    def our_callback(params, errors, best_params, best_error, index):
+        calls.append(index)
+        assert all(isinstance(p, dict) for p in params)
+        assert isinstance(errors, np.ndarray)
+        assert isinstance(best_params, dict)
+        assert isinstance(best_error, float)
+        assert isinstance(index, int)
+    results, errors = tf.fit(n_rounds=2,
+                             optimizer=n_opt,
+                             metric=metric,
+                             g=[1*nS, 30*nS],
+                             callback=our_callback)
+    assert len(calls) == 2
+
+    # Stop a fit via the callback
+
+    calls = []
+    def our_callback(params, errors, best_params, best_error, index):
+        calls.append(index)
+        assert all(isinstance(p, dict) for p in params)
+        assert isinstance(errors, np.ndarray)
+        assert isinstance(best_params, dict)
+        assert isinstance(best_error, float)
+        assert isinstance(index, int)
+        return True  # stop
+
+    results, errors = tf.fit(n_rounds=2,
+                             optimizer=n_opt,
+                             metric=metric,
+                             g=[1*nS, 30*nS],
+                             callback=our_callback)
+    assert len(calls) == 1
+
+
 def test_fitter_fit_errors(setup):
     dt, tf = setup
     with pytest.raises(TypeError):
@@ -219,7 +257,7 @@ def test_fitter_fit_errors(setup):
     with pytest.raises(TypeError):
         tf.fit(n_rounds=2,
                optimizer=n_opt,
-               metric=1,
+               metric=GammaFactor(3*ms, 60*ms),  # spike metric
                g=[1*nS, 30*nS])
 
 
@@ -570,14 +608,14 @@ def test_onlinetracefitter_init_errors(setup_online):
                           n_samples=10,
                           output=output_traces,
                           output_var='I',
-                          input_var='Exception',)
+                          input_var='Exception')
 
     with pytest.raises(Exception):
         OnlineTraceFitter(dt=0.1*ms, model=model, input=input_traces,
                           n_samples=10,
                           output=output_traces,
                           input_var='v',
-                          output_var='Exception',)
+                          output_var='Exception')
 
     with pytest.raises(Exception):
         OnlineTraceFitter(dt=0.1*ms, model=model, input=input_traces,
@@ -606,3 +644,14 @@ def test_onlinetracefitter_fit(setup_online):
     assert 'g' in results.keys()
 
     assert_equal(results, otf.best_params)
+
+
+def test_onlinetracefitter_generate_traces(setup_online):
+    dt, otf = setup_online
+    results, errors = otf.fit(n_rounds=2,
+                              optimizer=n_opt,
+                              g=[1 * nS, 30 * nS],
+                              restart=False, )
+    traces = otf.generate_traces()
+    assert isinstance(traces, np.ndarray)
+    assert_equal(np.shape(traces), np.shape(output_traces))