implemented Producer API and header, stub and tests. Builds cleanly, tests fail for now

tests/test_producer.cxx

@@ -0,0 +1,110 @@
+#include <gtest/gtest.h>
+
+#include <chrono>
+#include <fstream>
+
+#include "Producer.hpp"
+
+TEST(ProducerTest, ProducerCallsBackWhenEnabled)
+{
+  // Arrange create the file and write "1\n" into it.
+  {
+    std::ofstream out("fake_sysfs_input");
+    out << "1\n";
+  }
+  // create a fake callback function
+  std::vector<int> outputs;
+
+  // construct a producer with fake file and callback
+  Producer producer{"fake_sysfs_input", [&outputs](int value)
+                    { outputs.push_back(value); }, []() { return 42; }};
+  // Act: initialize producer and stop it.
+  producer.start();
+  std::this_thread::sleep_for(std::chrono::milliseconds(1));  // ← 1ms window
+  producer.stop();
+
+  // Assert: we expect one output being 42
+  ASSERT_EQ(outputs.size(), 1u);
+  EXPECT_EQ(outputs[0], 42);
+}
+
+TEST(ProducerTest, ProducerDoesNotCallWhenUnexpectedValue)
+{
+  // Arrange create the file and write "0\n" into it.
+  {
+    std::ofstream out("fake_sysfs_input");
+    out << "0\n";
+  }
+
+  std::vector<int> outputs;
+
+  Producer producer{"fake_sysfs_input",
+                    [&outputs](int value) { outputs.push_back(value); },
+                    []() { return 42; }, [](std::chrono::milliseconds) {}};
+
+  producer.start();
+  std::this_thread::sleep_for(std::chrono::milliseconds(1));  // ← 1ms window
+  producer.stop();
+
+  // Assert: we expect no output
+  EXPECT_TRUE(outputs.empty());
+}
+
+TEST(ProducerTest, ProducerDoesNotCallWhenEmpty)
+{
+  // Arrange create the file and write "0\n" into it.
+  {
+    std::ofstream out("fake_sysfs_input");
+    out << " ";
+  }
+
+  std::vector<int> outputs;
+
+  Producer producer{"fake_sysfs_input",
+                    [&outputs](int value) { outputs.push_back(value); },
+                    []() { return 42; }, [](std::chrono::milliseconds) {}};
+
+  producer.start();
+  producer.stop();
+
+  // Assert: we expect no output
+  EXPECT_TRUE(outputs.empty());
+}
+
+TEST(ProducerTest, ProducerDoesNotCallWhenUnreachable)
+{
+  std::vector<int> outputs;
+  std::vector<std::string> logs;
+
+  Producer producer{"nonexistant_sysfs_input",
+                    [&outputs](int value) { outputs.push_back(value); },
+                    []() { return 42; }, [](std::chrono::milliseconds) {}};
+
+  producer.start();
+  std::this_thread::sleep_for(std::chrono::milliseconds(1));  // ← 1ms window
+  producer.stop();
+
+  // Assert: we expect no output
+  EXPECT_TRUE(outputs.empty());
+}
+
+TEST(ProducerTest, ProducerDoesNotCallWhenTempTooHigh)
+{
+  // create  a file that contains error
+  {
+    std::ofstream out("fake_sysfs_input");
+    out << "error: temp too high";
+  }
+  std::vector<int> outputs;
+
+  Producer producer{"fake_sysfs_input",
+                    [&outputs](int value) { outputs.push_back(value); },
+                    []() { return 42; }, [](std::chrono::milliseconds) {}};
+
+  producer.start();
+  std::this_thread::sleep_for(std::chrono::milliseconds(1));  // ← 1ms window
+  producer.stop();
+
+  // Assert: we expect no output
+  EXPECT_TRUE(outputs.empty());
+}