tests: check for eigen in some tests

Author: james-d-mitchell

src/libsemigroups_pybind11/__init__.py

@@ -53,6 +53,7 @@
 
 try:
     from _libsemigroups_pybind11 import (
+        LIBSEMIGROUPS_EIGEN_ENABLED,
         LIBSEMIGROUPS_HPCOMBI_ENABLED,
         LIMIT_MAX,
         NEGATIVE_INFINITY,

tests/test_presentation_examples.py

@@ -13,6 +13,7 @@
 import pytest
 
 from libsemigroups_pybind11 import (
+    LIBSEMIGROUPS_EIGEN_ENABLED,
     POSITIVE_INFINITY,
     LibsemigroupsError,
     ReportGuard,
@@ -424,5 +425,6 @@ def test_braid_group():
 
     p = examples.braid_group(3)
     assert len(p.alphabet()) == 4
-    tc = ToddCoxeter(congruence_kind.twosided, p)
-    assert tc.number_of_classes() == POSITIVE_INFINITY
+    if LIBSEMIGROUPS_EIGEN_ENABLED:
+        tc = ToddCoxeter(congruence_kind.twosided, p)
+        assert tc.number_of_classes() == POSITIVE_INFINITY