cong: modify tests for upstream change

Specifically the changes in:

libsemigroups/libsemigroups#913

which change the number of runners in some Congruence objects, leading
to tests failing where the number or existence of certain runners is
assumed/required.

Author: james-d-mitchell

src/cong.cpp

@@ -67,9 +67,7 @@ individual algorithms, such as :any:`Kambites`,
     >>> cong = Congruence(congruence_kind.twosided, p)
     >>> is_obviously_infinite(cong)
     True
-    >>> cong.add_generating_pair([1, 1, 1], [])
-    <2-sided Congruence over <monoid presentation with 2 letters, 1 rule, and length 2> with 1 gen. pair, 4 runners>
-    >>> cong.number_of_classes()
+    >>> cong.add_generating_pair([1, 1, 1], []).number_of_classes()
     3
     >>> is_obviously_infinite(cong)
     False
@@ -250,7 +248,7 @@ obviously infinite; ``False`` is returned if it is not.
     congruence has infinitely many classes.
 )pbdoc");
     }  // bind_cong
-  }    // namespace
+  }  // namespace
 
   void init_cong(py::module& m) {
     bind_cong<word_type>(m, "CongruenceWord");

tests/test_cong.py

@@ -93,9 +93,10 @@ def test_has_get():
 
     c = Congruence(congruence_kind.twosided, p)
 
-    assert c.number_of_runners() == 4
-    assert c.has(ToddCoxeter)
-    tc = c.get(ToddCoxeter)
+    assert c.number_of_runners() <= 4
+    assert not c.has(ToddCoxeter)
+    assert c.has(Kambites)
+    k = c.get(Kambites)
 
     c.run()
     assert c.number_of_classes() == POSITIVE_INFINITY
@@ -104,9 +105,9 @@ def test_has_get():
     assert c.has(KnuthBendix)
     assert c.get(KnuthBendix).confluent()
 
-    # Check that the ToddCoxeter returned above outlives its deletion in
+    # Check that the Kambites returned above outlives its deletion in
     # Congruence
-    assert tc.number_of_classes() == POSITIVE_INFINITY
+    assert k.small_overlap_class() == 1
 
     with pytest.raises(LibsemigroupsError):
         c.get(ToddCoxeter)