Improve test coverage (#269)

These shouldn't be needed because the methods are actually hit. But
coverage doesn't see them for some reason.

Author: odow

test/MOI_wrapper.jl

@@ -1080,6 +1080,13 @@ function test_callback_error()
     @test_throws ErrorException("ABC") MOI.optimize!(model)
     return
 end
+function test_row_type()
+    @test HiGHS._row_type(MOI.GreaterThan(0.0)) == HiGHS._ROW_TYPE_GREATERTHAN
+    @test HiGHS._row_type(MOI.LessThan(0.0)) == HiGHS._ROW_TYPE_LESSTHAN
+    @test HiGHS._row_type(MOI.EqualTo(0.0)) == HiGHS._ROW_TYPE_EQUAL_TO
+    @test HiGHS._row_type(MOI.Interval(0.0, 1.0)) == HiGHS._ROW_TYPE_INTERVAL
+    return
+end
 
 end  # module