nboutin · February 22, 2023 13:24 · Feb 22, 2023 · Feb 22, 2023 · Feb 22, 2023
diff --git a/test.cpp b/test.cpp
@@ -2,6 +2,10 @@ TEST(alarm, checkAlarmAfter10Minutes) {
   time_fake t; // implements the time_interface
   output_fake o; // implements the output interface
   alarm_clock alarm(t, o);
+
   auto ring_time = t.now() + 10min;
   clock.set_alarm(ring_time);
+
+  t = t.now() + 10min; // We can increase our time
+  EXPECT_EQ(o.value(), "Alarm\n"); // We can check the output
 }
diff --git a/dependency_injection.cpp b/dependency_injection.cpp
@@ -2,6 +2,7 @@
 
 #include "time_interface.h"
 #include "output_interface.h"
+
 class alarm_clock {
 public:
   alarm_clock(const time_interface&, output_interface&)

diff --git a/dependency_injection.cpp b/dependency_injection.cpp
@@ -0,0 +1,29 @@
+// https://www.youtube.com/watch?v=zYPb7oBU5_E
+
+#include "time_interface.h"
+#include "output_interface.h"
+class alarm_clock {
+public:
+  alarm_clock(const time_interface&, output_interface&)
+  // ...
+  private:
+  // ...
+  const time_interface& time_;
+  output_interface& output_;
+};
+
+void alarm_clock::check_alarm() {
+  if (!is_active_) return;
+  if (now_is_approx_alarm_time()) {
+    ring_alarm();
+  }
+}
+
+bool alarm_clock::now_is_approx_alarm_time() const {
+  auto diff = abs(time_.now() - alarm_time_);
+  return (diff < 1s);
+}
+
+void alarm_clock::ring_alarm() {
+  output_ << "Alarm\n";
+}
diff --git a/main.cpp b/main.cpp
@@ -0,0 +1,7 @@
+int main() {
+  time_impl t; // implements the time_interface
+  output_console o; // implements the output_interface
+  alarm_clock alarm(t, o);
+  // ...
+  return 0;
+}
diff --git a/output_interface.h b/output_interface.h
@@ -0,0 +1,5 @@
+class output_interface {
+public:
+  virtual ~output_interface() = default;
+  virtual output_interface& operator<<(const string&) = 0;
+};
diff --git a/test.cpp b/test.cpp
@@ -0,0 +1,7 @@
+TEST(alarm, checkAlarmAfter10Minutes) {
+  time_fake t; // implements the time_interface
+  output_fake o; // implements the output interface
+  alarm_clock alarm(t, o);
+  auto ring_time = t.now() + 10min;
+  clock.set_alarm(ring_time);
+}
diff --git a/time_interface.h b/time_interface.h
@@ -0,0 +1,9 @@
+#include <chrono>
+
+class time_interface {
+public:
+  using time_point = std::chrono::time_point<std::chrono::system_clock>;
+
+  virtual ~time_interface() = default;
+  virtual time_point now() const = 0;
+};
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