Test failing online check against a mock HTTP server (#2598)

Author: mortenpi

test/online/Project.toml

@@ -1,7 +1,9 @@
 [deps]
 Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
+HTTP = "cd3eb016-35fb-5094-929b-558a96fad6f3"
 IOCapture = "b5f81e59-6552-4d32-b1f0-c071b021bf89"
 MarkdownAST = "d0879d2d-cac2-40c8-9cee-1863dc0c7391"
+Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 RegistryInstances = "2792f1a3-b283-48e8-9a74-f99dce5104f3"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 

test/online/online_linkcheck.jl

@@ -2,8 +2,21 @@ module OnlineLinkcheckTests
 using Documenter: Documenter, MarkdownAST, AbstractTrees
 using Documenter: linkcheck
 using Markdown
+using HTTP
 using Test
 
+PORT = rand(10_000:40_000)
+function lincheck_server_handler(req::HTTP.Request)
+    useragent = HTTP.header(req, "user-agent")
+    if startswith(useragent, "Mozilla/5.0")
+        return HTTP.Response(404)
+    elseif startswith(useragent, "curl")
+        return HTTP.Response(200)
+    end
+    return HTTP.Response(500)
+end
+server = HTTP.serve!(lincheck_server_handler, PORT)
+
 @testset "Online linkcheck" begin
 
     @testset "Successes" begin
@@ -25,14 +38,21 @@ using Test
     end
 
     @testset "Empty User-Agent" begin
+        # This used to point to
+        #
+        #   https://www.intel.com/content/www/us/en/developer/tools/oneapi/mpi-library.html)
+        #
+        # but now we use a mock HTTP server, to guarantee that the server's behavior doesn't change.
         src = convert(
             MarkdownAST.Node,
-            md"""
-            [Linkcheck Empty UA](https://www.intel.com/content/www/us/en/developer/tools/oneapi/mpi-library.html)
-            """
+            Markdown.parse(
+                """
+                [Linkcheck Empty UA](http://localhost:$(PORT)/content/www/us/en/developer/tools/oneapi/mpi-library.html)
+                """
+            )
         )
 
-        # The default user-agent fails (intel servers block it)
+        # The default user-agent fails (server blocks it, returns a 500)
         doc = Documenter.Document(; linkcheck = true, linkcheck_timeout = 20)
         doc.blueprint.pages["testpage"] = Documenter.Page("", "", "", [], Documenter.Globals(), src)
         @test_logs (:error,) @test linkcheck(doc) === nothing
@@ -65,4 +85,7 @@ using Test
 
 end
 
+# Close the mock HTTP server
+close(server)
+
 end # module