Add a check that bridge is used

Author: blegat

src/Bridges/Bridges.jl

@@ -303,17 +303,22 @@ function _runtests(
     model_eltype = eltype,
     print_inner_model::Bool = false,
     cannot_unbridge::Bool = false,
+    no_bridge_used::Bool = false,
 )
     # Load model and bridge it
     inner = MOI.Utilities.UniversalFallback(MOI.Utilities.Model{model_eltype}())
     model = _bridged_model(Bridge{eltype}, inner)
     input_fn(model)
+    _check_bridged(model; no_bridge_used)
     final_touch(model)
     # Should be able to call final_touch multiple times.
     final_touch(model)
     if print_inner_model
         print(inner)
     end
+    if no_bridge_used
+        return
+    end
     Test.@testset "Test outer bridged model appears like the input" begin       # COV_EXCL_LINE
         test =
             MOI.Utilities.UniversalFallback(MOI.Utilities.Model{model_eltype}())
@@ -512,6 +517,13 @@ function _general_bridge_tests(bridge::B) where {B<:AbstractBridge}
     return
 end
 
+function _check_bridged(model; no_bridge_used)
+    unused = isempty(MOI.Bridges.Variable.bridges(model)) &&
+        isempty(MOI.Bridges.Constraint.bridges(model)) &&
+        isempty(MOI.Bridges.Objective.bridges(model))
+    Test.@test unused == no_bridge_used
+end
+
 """
     BridgeRequiresFiniteDomainError{
         B<:AbstractBridge,

test/Bridges/Constraint/IndicatorSOS1Bridge.jl

@@ -345,6 +345,7 @@ function test_runtests()
         [z, 2.0 * x * x] in Indicator{ACTIVATE_ON_ONE}(LessThan(2.0))
         z in ZeroOne()
         """,
+        no_bridge_used = true,
     )
     return
 end

test/Bridges/Constraint/NumberConversionBridge.jl

@@ -104,6 +104,7 @@ function test_runtests()
         variables: x
         ::Float64: [x, x] in Zeros(2)
         """,
+        no_bridge_used = true,
     )
     # VectorAffineFunction
     MOI.Bridges.runtests(