test_sampler.cpp: put in code for sampler test

tests/sampler/test_sampler.cpp

@@ -1 +1,66 @@
+#include <iostream>
+#include <sstream>
+#include <vector>
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
 
+#include "Kokkos_Core.hpp"
+
+struct Tester {
+  template <typename execution_space>
+  explicit Tester(const execution_space& space) {
+    //! Explicitly launch a kernel with a name, and run it 150 times with kernel
+    //! logger. Use a periodic sampling with skip rate 51. This should print
+    //! out 2 invocation, and there is a single matcher with a regular
+    //! expression to check this.
+
+    for (int iter = 0; iter < 150; iter++) {
+      Kokkos::parallel_for("named kernel",
+                           Kokkos::RangePolicy<execution_space>(space, 0, 1),
+                           *this);
+    }
+  }
+
+  KOKKOS_FUNCTION void operator()(const int) const {}
+};
+
+static const std::vector<std::string> matchers{
+    "(.*)KokkosP: sample 51 calling child-begin function...(.*)",
+    "(.*)KokkosP: sample 51 finished with child-begin function.(.*)",
+    "(.*)KokkosP: sample 51 calling child-end function...(.*)",
+    "(.*)KokkosP: sample 51 calling child-end function.(.*)",
+    "(.*)KokkosP: sample 102 calling child-begin function...(.*)",
+    "(.*)KokkosP: sample 102 finished with child-begin function.(.*)",
+    "(.*)KokkosP: sample 102 calling child-end function...(.*)",
+    "(.*)KokkosP: sample 102 calling child-end function.(.*)"};
+
+/**
+ * @test This test checks that the tool effectively samples.
+ *
+
+ */
+TEST(SamplerTest, ktoEnvVarDefault) {
+  //! Initialize @c Kokkos.
+  Kokkos::initialize();
+
+  //! Redirect output for later analysis.
+  std::cout.flush();
+  std::ostringstream output;
+  std::streambuf* coutbuf = std::cout.rdbuf(output.rdbuf());
+
+  //! Run tests. @todo Replace this with Google Test.
+  Tester tester(Kokkos::DefaultExecutionSpace{});
+
+  //! Finalize @c Kokkos.
+  Kokkos::finalize();
+
+  //! Restore output buffer.
+  // std::cout.flush();
+  std::cout.rdbuf(coutbuf);
+  std::cout << output.str() << std::endl;
+
+  //! Analyze test output.
+  for (const auto& matcher : matchers) {
+    EXPECT_THAT(output.str(), ::testing::ContainsRegex(matcher));
+  }  // end TEST
+}