Test u_str error messages

Author: MilesCranmer

src/uparse.jl

@@ -82,7 +82,7 @@ function map_to_scope(sym::Symbol)
     if sym in UNIT_SYMBOLS
         return lookup_unit(sym)
     elseif sym in CONSTANT_SYMBOLS
-        throw(ArgumentError("Found the symbol $sym. To access constants in a unit expression, access the `Constants` module. For example, `u\"Constants.h\"`."))
+        throw(ArgumentError("Symbol $sym found in `Constants` but not `Units`. Please access the `Constants` module. For example, `u\"Constants.$sym\"`."))
         return sym
     else
         throw(ArgumentError("Symbol $sym not found in `Units` or `Constants`."))

test/unittests.jl

@@ -471,7 +471,9 @@ end
     @test typeof(u"fm") == DEFAULT_QUANTITY_TYPE
     @test typeof(u"fm"^2) == DEFAULT_QUANTITY_TYPE
 
-    @test_throws ArgumentError eval(:(u":x"))
+    @test_throws LoadError eval(:(u"x"))
+    VERSION >= v"1.9" && @test_throws "Symbol x not found" uparse("x")
+    VERSION >= v"1.9" && @test_throws "Symbol c found in `Constants` but not `Units`" uparse("c")
 end
 
 @testset "Constants" begin