add test for generated docs

test/advanced.jl

@@ -102,3 +102,46 @@ using Test  #src
 @test Interfaces.test(Group.GroupInterface, Float64)  #src
 @test !Interfaces.test(Group.GroupInterface, Int, int_pairs)  #src
 @test_throws ArgumentError Interfaces.test(Group.GroupInterface, Float64, int_pairs)  #src
+
+# Test generated docs
+expected_extended_help = """# Extended help
+
+## Mandatory keys:
+
+* `neutral_check`:
+  * neutral stable
+* `multiplication_check`:
+  * multiplication stable
+* `inversion_check`:
+  * inversion stable
+  * inversion works"""
+
+@test strip(Interfaces.extended_help(Group.GroupInterface)) == strip(expected_extended_help)
+
+
+expected_docs = """```
+    GroupInterface
+```
+
+An Interfaces.jl `Interface` with mandatory components `(:neutral_check, :multiplication_check, :inversion_check)` and optional components `()`.
+
+A group is a set of elements with a neutral element where you can perform multiplications and inversions.
+
+The conditions checking the interface accept an `Arguments` object with two fields named `x` and `y`. The type of the first field `x` must be the type you wish to declare as implementing `GroupInterface`.
+
+# Extended help
+
+## Mandatory keys:
+
+  * `neutral_check`:
+
+      * neutral stable
+  * `multiplication_check`:
+
+      * multiplication stable
+  * `inversion_check`:
+
+      * inversion stable
+      * inversion works"""
+
+@test strip(string(@doc Group.GroupInterface)) == strip(expected_docs)