test: Add some simple tests for Bpm class

CMakeLists.txt

@@ -1475,6 +1475,7 @@ add_executable(mixxx-test
   src/test/beatgridtest.cpp
   src/test/beatmaptest.cpp
   src/test/beatstranslatetest.cpp
+  src/test/bpmtest.cpp
   src/test/bpmcontrol_test.cpp
   src/test/broadcastprofile_test.cpp
   src/test/broadcastsettings_test.cpp

src/test/bpmtest.cpp

@@ -0,0 +1,26 @@
+#include <gtest/gtest.h>
+
+#include <QDebug>
+
+#include "track/bpm.h"
+
+class BpmTest : public testing::Test {
+};
+
+TEST_F(BpmTest, TestBpmEquality) {
+    EXPECT_EQ(mixxx::Bpm(120), mixxx::Bpm(120));
+    EXPECT_EQ(mixxx::Bpm(120), mixxx::Bpm(60) * 2);
+    EXPECT_EQ(mixxx::Bpm(120), mixxx::Bpm(240) / 2);
+
+    // Verify that invalid values are equal to each other, regardless of their
+    // actual value.
+    EXPECT_EQ(mixxx::Bpm(mixxx::Bpm::kValueUndefined), mixxx::Bpm());
+    EXPECT_EQ(mixxx::Bpm(0.0), mixxx::Bpm());
+    EXPECT_EQ(mixxx::Bpm(-120.0), mixxx::Bpm());
+    EXPECT_EQ(mixxx::Bpm(-120.0), mixxx::Bpm(0.0));
+    EXPECT_EQ(mixxx::Bpm(-120.0), mixxx::Bpm(-100.0));
+
+    // Verify that valid and invalid values are not equal
+    EXPECT_NE(mixxx::Bpm(120.0), mixxx::Bpm());
+    EXPECT_NE(mixxx::Bpm(120.0), mixxx::Bpm(-120.0));
+}