Semigroups breaks testbugfix/2018-05-09-submagma.tst in GAP master branch

[olexandr-konovalov]

This bugfix test is not present in stable-4.9 branch. When make testbugfix is executed in the master branch, then the following happens:

gap> Test("tst/testbugfix/2018-05-09-submagma.tst");
true                                
gap> LoadPackage("semigroups":OnlyNeeded);
------------------------------------------------------------------------------------
Loading  orb 4.8.0 (Methods to enumerate orbits)
by Juergen Mueller (http://www.math.rwth-aachen.de/~Juergen.Mueller),
   Max Neunh?ffer (http://www-groups.mcs.st-and.ac.uk/~neunhoef), and
   Felix Noeske (http://www.math.rwth-aachen.de/~Felix.Noeske).
Homepage: https://gap-packages.github.io/orb
------------------------------------------------------------------------------------
------------------------------------------------------------------------------------
Loading  Digraphs 0.12.1 (Digraphs - Methods for digraphs)
by J. De Beule (http://homepages.vub.ac.be/~jdbeule/),
   J. Jonusas (http://www-groups.mcs.st-andrews.ac.uk/~julius/),
   J. D. Mitchell (http://goo.gl/ZtViV6),
   M. Torpey (http://www-groups.mcs.st-andrews.ac.uk/~mct25/), and
   W. A. Wilson (http://www-groups.mcs.st-andrews.ac.uk/~waw7/).
Homepage: https://gap-packages.github.io/Digraphs
------------------------------------------------------------------------------------
------------------------------------------------------------------------------------
Loading  genss 1.6.5 (Generic Schreier-Sims)
by Max Neunh?ffer (http://www-groups.mcs.st-and.ac.uk/~neunhoef) and
   Felix Noeske (http://www.math.rwth-aachen.de/~Felix.Noeske).
Homepage: https://gap-packages.github.io/genss
------------------------------------------------------------------------------------
-----------------------------------------------------------------------------
Loading  Semigroups 3.0.16
by J. D. Mitchell (http://www-groups.mcs.st-andrews.ac.uk/~jamesm/)
with contributions by:
     S. Burrell (http://sburrell.nfshost.com),
     M. Delgado (http://cmup.fc.up.pt/cmup/mdelgado/),
     J. East (http://goo.gl/MuiJu5),
     A. Egri-Nagy (http://www.egri-nagy.hu),
     N. Ham (https://n-ham.github.io),
     J. Jonusas (http://www-groups.mcs.st-andrews.ac.uk/~julius/),
     M. Pfeiffer (https://www.morphism.de/~markusp/),
     C. Russell,
     B. Steinberg (http://www.sci.ccny.cuny.edu/~benjamin/),
     F. Smith,
     J. Smith (http://math.sci.ccny.cuny.edu/people?name=Jhevon_Smith),
     M. Torpey (http://www-groups.mcs.st-and.ac.uk/~mct25/),
 and W. A. Wilson (http://wilf.me).
-----------------------------------------------------------------------------
true
gap> Test("tst/testbugfix/2018-05-09-submagma.tst");
########> Diff in tst/testbugfix/2018-05-09-submagma.tst:33
# Input is:
mgm:=Magma( () );
# Expected output:
<commutative semigroup with 1 generator>
# But found:
<trivial group with 1 generator>
########
########> Diff in tst/testbugfix/2018-05-09-submagma.tst:41
# Input is:
IsMagmaWithInverses(mgm);
# Expected output:
false
# But found:
true
########
false
gap> 

[james-d-mitchell]

So, if I do the following in GAP stable-4.9 with no packages loaded:

gap> mgm := Magma(());
<group with 1 generator>
gap> IsMagmaWithInverses(mgm);
true
gap>  IsGroup(mgm);
true

So maybe this is an issue of changed behaviour in GAP master, rather than an issue with Semigroups per say?

[olexandr-konovalov]

We need to see. This test has been added gap-system/gap@2e29846#diff-1bd3f64ee92c1c0ac5ed494bcee48753 with a fix of gap-system/gap#2400

[wilfwilson]

Resolved by gap-system/gap#2796.