rot13: Autodetect bonus macros in tests (JuliaLang#231)

This means markers and users don't need to fiddle with the tests file.

exercises/rotational-cipher/README.md

@@ -34,7 +34,7 @@ This is a good exercise to experiment with non-standard string literals and meta
 
 A short introduction to non-standard string literals can be found in this [blog post](https://web.archive.org/web/20170625222109/https://iaindunning.com/blog/julia-unicode.html). A detailed metaprogramming guide can be found in the [manual](https://docs.julialang.org/en/v1/manual/metaprogramming/).
 
-You can extend your solution by adding the functionality described below. To test your solution, you have to remove the comments at the end of `runtests.jl` before running the tests as usual.
+You can extend your solution by adding the functionality described below.
 
 Bonus A only requires basics as outlined in the blog post. Bonus B requires significantly more knowledge of metaprogramming in Julia.
 

exercises/rotational-cipher/runtests.jl

@@ -34,18 +34,21 @@ end
 
 # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 # Additional exercises                                                        #
-# Change @test_skip to @test for the optional bonus exercises from HINTS.md   #
 # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
 # Bonus A
-@testset "Bonus A: string literal R13" begin
-    @test_skip R13"The quick brown fox jumps over the lazy dog." == "Gur dhvpx oebja sbk whzcf bire gur ynml qbt."
+if isdefined(Main, Symbol("@R13_str"))
+    @eval @testset "Bonus A: string literal R13" begin
+        @test R13"The quick brown fox jumps over the lazy dog." == "Gur dhvpx oebja sbk whzcf bire gur ynml qbt."
+    end
 end
 
 # Bonus B
-@testset "Bonus B: string literals" begin
-    @test_skip R5"OMG" == "TRL"
-    @test_skip R4"Testing 1 2 3 testing" == "Xiwxmrk 1 2 3 xiwxmrk"
-    @test_skip R21"Let's eat, Grandma!" == "Gzo'n zvo, Bmviyhv!"
-    @test_skip R13"The quick brown fox jumps over the lazy dog." == "Gur dhvpx oebja sbk whzcf bire gur ynml qbt."
+if isdefined(Main, Symbol("@R1_str"))
+    @eval @testset "Bonus B: string literals" begin
+        @test R5"OMG" == "TRL"
+        @test R4"Testing 1 2 3 testing" == "Xiwxmrk 1 2 3 xiwxmrk"
+        @test R21"Let's eat, Grandma!" == "Gzo'n zvo, Bmviyhv!"
+        @test R13"The quick brown fox jumps over the lazy dog." == "Gur dhvpx oebja sbk whzcf bire gur ynml qbt."
+    end
 end