add a basic libmain test for the progress bar rendering

Hooray for leaky abstraction allowing us to test this particular part of
the render pipeline.

Change-Id: Ie0f251ff874f63324e6a9c6388b84ec6507eeae2

src/libmain/progress-bar.hh

@@ -13,9 +13,8 @@ constexpr const auto A_LONG_TIME = std::chrono::duration_cast<std::chrono::milli
     100 * 365 * std::chrono::seconds(86400)
 );
 
-class ProgressBar : public Logger
+struct ProgressBar : public Logger
 {
-private:
     struct ActInfo
     {
         using TimePoint = std::chrono::time_point<std::chrono::steady_clock>;
@@ -66,8 +65,6 @@ private:
     bool printBuildLogs = false;
     bool isTTY;
 
-public:
-
     ProgressBar(bool isTTY)
         : isTTY(isTTY)
     {

tests/unit/libmain/progress-bar.cc

@@ -0,0 +1,43 @@
+#include <gtest/gtest.h>
+
+#include "eval.hh"
+#include "progress-bar.hh"
+#include "logging.hh"
+#include "shared.hh"
+
+constexpr std::string_view TEST_URL = "https://github.com/NixOS/nixpkgs/archive/master.tar.gz";
+// Arbitrary number. We picked the size of a Nixpkgs tarball that we downloaded.
+constexpr uint64_t TEST_EXPECTED = 43'370'307;
+// Arbitrary number. We picked the progress made on a Nixpkgs tarball download we interrupted.
+constexpr uint64_t TEST_DONE = 1'787'251;
+
+constexpr std::string_view EXPECTED = ANSI_GREEN "1.7" ANSI_NORMAL "/41.4 MiB DL";
+// Mostly here for informational purposes, but also if we change the way the escape codes
+// are defined this test might break in some annoying to debug way.
+constexpr std::string_view EXPECTED_RAW = "\x1b[32;1m1.7\x1b[0m/41.4 MiB DL";
+static_assert(EXPECTED == EXPECTED_RAW, "Hey, hey, the ANSI escape code definitions prolly changed");
+
+namespace nix
+{
+    TEST(ProgressBar, basicStatusRender) {
+        initNix();
+        initGC();
+
+        startProgressBar();
+        ASSERT_NE(dynamic_cast<ProgressBar *>(logger), nullptr);
+        ProgressBar & progressBar = dynamic_cast<ProgressBar &>(*logger);
+
+        Activity act(
+            progressBar,
+            lvlDebug,
+            actFileTransfer,
+            fmt("downloading '%s'", TEST_URL),
+            { "https://github.com/NixOS/nixpkgs/archive/master.tar.gz" }
+        );
+        act.progress(TEST_DONE, TEST_EXPECTED);
+        auto state = progressBar.state_.lock();
+        std::string const renderedStatus = progressBar.getStatus(*state);
+
+        ASSERT_EQ(renderedStatus, EXPECTED);
+    }
+}

tests/unit/meson.build

@@ -249,3 +249,25 @@ test(
   suite : 'check',
   protocol : 'gtest',
 )
+
+libmain_tester = executable(
+  'liblixmain-tests',
+  files('libmain/progress-bar.cc'),
+  dependencies : [
+    liblixmain,
+    liblixexpr,
+    liblixutil,
+    liblixstore,
+    gtest,
+    boost,
+  ],
+  cpp_pch : cpp_pch,
+)
+
+test(
+  'libmain-unit-tests',
+  libmain_tester,
+  args : tests_args,
+  suite : 'check',
+  protocol : 'gtest',
+)