fix(ssr): Include full model in model selection list.

Also, hack SSR through tests that provide single-feature data in the same
way that trapping was handled.

pysindy/optimizers/ssr.py

@@ -194,8 +194,10 @@ def _reduce(self, x, y):
                 " ... {: >10} ... {: >10}".format(*row)
             )
 
-        self.history_ = []
-        self.err_history_ = []
+        self.history_ = [coef]
+        self.err_history_ = [
+            np.sum((y - x @ coef.T) ** 2) + l0_penalty * np.count_nonzero(coef)
+        ]
         for k in range(self.max_iter):
             for i in range(n_targets):
                 if self.criteria == "coefficient_value":

test/test_optimizers/test_optimizers.py

@@ -79,6 +79,8 @@ def _align_optimizer_and_1dfeatures(
     if isinstance(opt, TrappingSR3):
         opt = TrappingSR3(_n_tgts=1, _include_bias=False)
         features = np.hstack([features, features])
+    elif isinstance(opt, SSR):
+        features = np.hstack([features, features])
     else:
         features = features
     return opt, features