Thank you for review! Diff between two last patches and new patch
below.

+--
+-- Check that _space, _index and _sequence have the same number of
+-- records.
+--
+space_count == #box.space._space:select()
+index_count == #box.space._index:select()
+sequence_count == #box.space._sequence:select()
+
+box.schema.user.drop('tmp’)

I see no tests involving FK constraints. Add them as well.

Added.

diff --git a/test/sql/drop-table.test.lua b/test/sql/drop-table.test.lua
index 1bc8894..f86e3d8 100644
--- a/test/sql/drop-table.test.lua
+++ b/test/sql/drop-table.test.lua

+-- Give user right to write in _sequence. Still have not enough
+-- rights to write in _fk_constraint.
+--
+box.schema.user.grant('tmp', 'write', 'space', '_sequence')
+box.session.su('tmp')
+
+box.sql.execute('CREATE TABLE t3(a INTEGER PRIMARY KEY);')
+--
+-- Error: user do not have rights to write in _fk_constraint.
+--
+box.sql.execute('CREATE TABLE t4(x INTEGER PRIMARY KEY REFERENCES t3);')
+box.sql.execute('DROP TABLE t3;’)

You misunderstood me a bit. I mean following test:

fk_count = #box.space._fk_constraints:select()

box.sql.execute('CREATE TABLE t4(x INTEGER PRIMARY KEY REFERENCES t3, a INT UNIQUE, c INT REFERENCES t3);’)

Here creation of last FK fails - for instance due to type mismatch.

Then, number of created FK constraints (and indexes) should be unchanged:

fk_count == #box.space._fk_constraints:select()

index_count == #box.space._fk_constraints:select()

Note that FK constraints are created after indexes.