Fix testing of warning messages

Author: MilesCranmer

test/test_deprecations.jl

@@ -8,13 +8,16 @@ tree = cos(2.1 * x1)
 
 # Also test warnings:
 for constructor in (OperatorEnum, GenericOperatorEnum)
-    operators = constructor(; binary_operators=[+, -, *, /], unary_operators=[cos, sin])
     VERSION >= v"1.9" &&
-        @test_warn "The `tree(X; kws...)` syntax is deprecated" tree([1.0; 2.0;;])
+        @test_logs (:warn, r"The `tree\(X; kws...\)` syntax is deprecated.*") tree(
+            [1.0; 2.0;;]
+        )
 
     constructor == GenericOperatorEnum && continue
 
     tree'([1.0; 2.0;;])
     VERSION >= v"1.9" &&
-        @test_warn "The `tree(X; kws...)` syntax is deprecated" tree'([1.0; 2.0;;])
+        @test_logs (:warn, r"The `tree'\(X; kws...\)` syntax is deprecated.*") tree'(
+            [1.0; 2.0;;]
+        )
 end

test/test_evaluation.jl

@@ -170,7 +170,7 @@ end
         return x^2
     end for i in 1:num_ops]
     operators = if VERSION >= v"1.9"
-        @test_warn "You have passed over 15 binary" OperatorEnum(;
+        @test_logs (:warn, r"You have passed over 15 binary.*") OperatorEnum(;
             binary_operators, unary_operators
         )
     else
@@ -183,7 +183,9 @@ end
     @test truth ≈ tree(X, operators)
 
     VERSION >= v"1.9" &&
-        @test_warn "You have passed over 15 unary" OperatorEnum(; unary_operators)
+        @test_logs (:warn, r"You have passed over 15 unary.*") OperatorEnum(;
+            unary_operators
+        )
 
     # This OperatorEnum will trigger the fallback code for fast compilation.
     many_ops_operators = OperatorEnum(;