Implement a repl characterization test system

This allows for automating using the repl without needing a PTY, with
very easy to write test files.

Change-Id: Ia8d7854edd91f93477638942cb6fc261354e6035

1 files changed, 69 insertions, 0 deletions

diff --git a/tests/functional/repl_characterization/test-session.hh b/tests/functional/repl_characterization/test-session.hh
new file mode 100644
index 000000000..19636640b
--- /dev/null
+++ b/tests/functional/repl_characterization/test-session.hh
@@ -0,0 +1,69 @@
+#pragma once
+///@file
+
+#include <sched.h>
+#include <string>
+
+#include "util.hh"
+#include "tests/terminal-code-eater.hh"
+
+namespace nix {
+
+struct RunningProcess
+{
+    pid_t pid;
+    Pipe procStdin;
+    Pipe procStdout;
+
+    static RunningProcess start(std::string executable, Strings args);
+};
+
+/** DFA that catches repl prompts */
+class ReplOutputParser
+{
+public:
+    ReplOutputParser(std::string prompt)
+        : prompt(prompt)
+    {
+        assert(!prompt.empty());
+    }
+    /** Feeds in a character and returns whether this is an open prompt */
+    bool feed(char c);
+
+    enum class State {
+        Prompt,
+        Context,
+    };
+
+private:
+    State state = State::Prompt;
+    size_t pos_in_prompt = 0;
+    std::string const prompt;
+
+    void transition(State state, char responsible_char, bool wasPrompt = false);
+};
+
+struct TestSession
+{
+    RunningProcess proc;
+    ReplOutputParser outputParser;
+    TerminalCodeEater eater;
+    std::string outLog;
+    std::string prompt;
+
+    TestSession(std::string prompt, RunningProcess && proc)
+        : proc(std::move(proc))
+        , outputParser(prompt)
+        , eater{}
+        , outLog{}
+        , prompt(prompt)
+    {
+    }
+
+    bool waitForPrompt();
+
+    void runCommand(std::string command);
+
+    void close();
+};
+};