3 files changed, 113 insertions, 3 deletions
diff --git a/build/test/operation.cxx b/build/test/operation.cxx
index 75e3e80..da98e7d 100644
--- a/build/test/operation.cxx
+++ b/build/test/operation.cxx
@@ -25,7 +25,7 @@ namespace build
       "test",
       "test",
       "testing",
-      "tested",
+      "has nothing to test", // We cannot "be tested".
       execution_mode::first,
       &test_pre,
       nullptr
diff --git a/build/test/rule b/build/test/rule
index db10606..259b72b 100644
--- a/build/test/rule
+++ b/build/test/rule
@@ -23,6 +23,9 @@ namespace build
       virtual recipe
       apply (action, target&, const match_result&) const;
 
+      static target_state
+      perform_test (action, target&);
+
     private:
       operation_id test_id;
     };
diff --git a/build/test/rule.cxx b/build/test/rule.cxx
index 3fd3a16..91ddb4f 100644
--- a/build/test/rule.cxx
+++ b/build/test/rule.cxx
@@ -4,12 +4,16 @@
 
 #include <build/test/rule>
 
+#include <butl/process>
+#include <butl/fdstream>
+
 #include <build/scope>
 #include <build/target>
 #include <build/algorithm>
 #include <build/diagnostics>
 
 using namespace std;
+using namespace butl;
 
 namespace build
 {
@@ -38,12 +42,115 @@ namespace build
     }
 
     recipe rule::
-    apply (action, target&, const match_result& mr) const
+    apply (action a, target&, const match_result& mr) const
     {
       if (!mr.value) // Not a test.
         return noop_recipe;
 
-      return noop_recipe; //@@ TMP
+      return a == action (perform_id, test_id)
+        ? &perform_test
+        : noop_recipe; // Don't do anything for other meta-operations.
+    }
+
+    // The format of args shall be:
+    //
+    // name1 arg arg ... nullptr
+    // name2 arg arg ... nullptr
+    // ...
+    // nameN arg arg ... nullptr nullptr
+    //
+    static bool
+    pipe_process (char const** args, process* prev = nullptr)
+    {
+      // Find the next process, if any.
+      //
+      char const** next (args);
+      for (next++; *next != nullptr; next++) ;
+      next++;
+
+      // Redirect stdout to a pipe unless we are last, in which
+      // case redirect it to stderr.
+      //
+      int out (*next == nullptr ? 2 : -1);
+      bool pr, wr;
+
+      if (prev == nullptr)
+      {
+        // First process.
+        //
+        process p (args, 0, out);
+        pr = *next == nullptr || pipe_process (next, &p);
+        wr = p.wait ();
+      }
+      else
+      {
+        // Next process.
+        //
+        process p (args, *prev, out);
+        pr = *next == nullptr || pipe_process (next, &p);
+        wr = p.wait ();
+      }
+
+      if (!wr)
+      {
+        // @@ Needs to go into the same diag record.
+        //
+        error << "non-zero exit status from:";
+        print_process (args);
+      }
+
+      return pr && wr;
+    }
+
+
+    target_state rule::
+    perform_test (action, target& t)
+    {
+      // @@ Would be nice to print what signal/core was dumped.
+      //
+
+      // @@ Doesn't have to be a file target if we have test.cmd.
+      //
+      file& ft (static_cast<file&> (t));
+      assert (!ft.path ().empty ()); // Should have been assigned by update.
+
+      cstrings args {ft.path ().string ().c_str (), nullptr};
+
+      args.push_back ("diff");
+      args.push_back ("-u");
+      args.push_back ("test.std");
+      args.push_back ("-");
+      args.push_back (nullptr);
+
+      args.push_back (nullptr); // Second.
+
+      if (verb)
+        print_process (args);
+      else
+        text << "test " << t;
+
+      try
+      {
+        if (!pipe_process (args.data ()))
+        {
+          //@@ Need to use the same diag record.
+          //
+          error << "failed test:";
+          print_process (args);
+          throw failed ();
+        }
+
+        return target_state::changed;
+      }
+      catch (const process_error& e)
+      {
+        error << "unable to execute " << args[0] << ": " << e.what ();
+
+        if (e.child ())
+          exit (1);
+
+        throw failed ();
+      }
     }
   }
 }