[tools/dspec_tester.d] Test articles directory (#4203)

Also find RUNNABLE_EXAMPLE_COMPILE and RUNNABLE_EXAMPLE_FAIL tests in `std`.

Author: ntrel

articles/cpptod.dd

@@ -928,7 +928,7 @@ void main()
 
     auto d2 = gallery[0];
     d2.id = 1;
-    assert(d2.id == gallery[0].id, "neither ref nor pointer");
+    assert(d2.id != gallery[0].id); // d2 is neither ref nor pointer
 }
 ------
 )

tools/dspec_tester.d

@@ -72,7 +72,10 @@ unittest
 
 auto findDdocMacro(R)(R text, string ddocKey)
 {
-    return text.splitter(ddocKey).map!untilClosingParentheses.dropOne;
+    auto sr = text.splitter(ddocKey);
+    // don't let RUNNABLE_EXAMPLE match RUNNABLE_EXAMPLE_FOO
+    auto fr = sr.filter!(s => s.length ? s[0] != '_' : true);
+    return fr.map!untilClosingParentheses.dropOne;
 }
 
 auto ddocMacroToCode(R)(R text)
@@ -95,6 +98,7 @@ int main(string[] args)
 
     const rootDir = __FILE_FULL_PATH__.dirName.dirName;
     const specDir = rootDir.buildPath("spec");
+    const articlesDir = rootDir.buildPath("articles");
     const stdDir = rootDir.buildPath("..", "phobos", "std");
 
     config.dmdBinPath = environment.get("DMD", "dmd");
@@ -117,9 +121,12 @@ int main(string[] args)
         SpecType("$(SPEC_RUNNABLE_EXAMPLE_COMPILE", CompileConfig.TestMode.compile),
         SpecType("$(SPEC_RUNNABLE_EXAMPLE_RUN", CompileConfig.TestMode.run),
         SpecType("$(SPEC_RUNNABLE_EXAMPLE_FAIL", CompileConfig.TestMode.fail),
+        SpecType("$(RUNNABLE_EXAMPLE_COMPILE", CompileConfig.TestMode.compile),
         SpecType("$(RUNNABLE_EXAMPLE", CompileConfig.TestMode.run),
+        SpecType("$(RUNNABLE_EXAMPLE_FAIL", CompileConfig.TestMode.fail),
     ];
     auto files = chain(specDir.dirEntries("*.dd", SpanMode.depth),
+        articlesDir.dirEntries("*.dd", SpanMode.depth),
         stdDir.dirEntries("*.d", SpanMode.depth));
     shared bool hasFailed;
     foreach (file; files.parallel(1))