Add tests

stdlib/REPL/test/repl.jl

@@ -1093,13 +1093,31 @@ Short docs
 Long docs
 """
 f() = nothing
+@doc text"""
+    f_plain()
+
+Plain text docs
+"""
+f_plain() = nothing
+@doc html"""
+<h1><code>f_html()</code></h1>
+<p>HTML docs.</p>
+"""
+f_html() = nothing
 end # module BriefExtended
+
 buf = IOBuffer()
 md = Base.eval(REPL._helpmode(buf, "$(@__MODULE__).BriefExtended.f"))
 @test length(md.content) == 2 && isa(md.content[2], REPL.Message)
 buf = IOBuffer()
 md = Base.eval(REPL._helpmode(buf, "?$(@__MODULE__).BriefExtended.f"))
 @test length(md.content) == 1 && length(md.content[1].content[1].content) == 4
+buf = IOBuffer()
+txt = Base.eval(REPL._helpmode(buf, "$(@__MODULE__).BriefExtended.f_plain"))
+@test !isempty(sprint(show, txt))
+buf = IOBuffer()
+html = Base.eval(REPL._helpmode(buf, "$(@__MODULE__).BriefExtended.f_html"))
+@test !isempty(sprint(show, html))
 
 # PR #27562
 fake_repl() do stdin_write, stdout_read, repl