diff --git a/tests/src/helpers/metric_value_helpers.hpp b/tests/src/helpers/metric_value_helpers.hpp
new file mode 100644
index 0000000..f21d42a
--- /dev/null
+++ b/tests/src/helpers/metric_value_helpers.hpp
@@ -0,0 +1,17 @@
+#pragma once
+
+#include "metric_value.hpp"
+
+#include <gmock/gmock.h>
+
+inline void PrintTo(const MetricValue& o, std::ostream* os)
+{
+    (*os) << "{ id: " << o.id << ", metadata: " << o.metadata
+          << ", value: " << o.value << ", timestamp: " << o.timestamp << " }";
+}
+
+inline bool operator==(const MetricValue& left, const MetricValue& right)
+{
+    return std::tie(left.id, left.metadata, left.value, left.timestamp) ==
+           std::tie(right.id, right.metadata, right.value, right.timestamp);
+}
\ No newline at end of file
diff --git a/tests/src/helpers/sensor_id_helpers.hpp b/tests/src/helpers/sensor_id_helpers.hpp
new file mode 100644
index 0000000..9b59d22
--- /dev/null
+++ b/tests/src/helpers/sensor_id_helpers.hpp
@@ -0,0 +1,22 @@
+#pragma once
+
+#include "interfaces/sensor.hpp"
+
+#include <gmock/gmock.h>
+
+namespace interfaces
+{
+
+inline void PrintTo(const Sensor::Id& o, std::ostream* os)
+{
+    (*os) << "{ type: " << o.type << ", service: " << o.service
+          << ", path: " << o.path << " }";
+}
+
+inline bool operator==(const Sensor::Id& left, const Sensor::Id& right)
+{
+    return std::tie(left.type, left.service, left.path) ==
+           std::tie(right.type, right.service, right.path);
+}
+
+} // namespace interfaces
\ No newline at end of file
diff --git a/tests/src/mocks/metric_mock.hpp b/tests/src/mocks/metric_mock.hpp
index d3d9e64..21f7733 100644
--- a/tests/src/mocks/metric_mock.hpp
+++ b/tests/src/mocks/metric_mock.hpp
@@ -15,6 +15,7 @@
             .WillByDefault(ReturnRefOfCopy(std::vector<MetricValue>()));
     }
 
+    MOCK_METHOD(void, initialize, (), (override));
     MOCK_METHOD(const std::vector<MetricValue>&, getReadings, (),
                 (const, override));
     MOCK_METHOD(nlohmann::json, to_json, (), (const, override));
diff --git a/tests/src/mocks/sensor_mock.hpp b/tests/src/mocks/sensor_mock.hpp
index 0dcb2b5..d71d77e 100644
--- a/tests/src/mocks/sensor_mock.hpp
+++ b/tests/src/mocks/sensor_mock.hpp
@@ -8,11 +8,14 @@
 class SensorMock : public interfaces::Sensor
 {
   public:
+    explicit SensorMock()
+    {
+        initialize();
+    }
+
     explicit SensorMock(Id sensorId) : mockSensorId(sensorId)
     {
-        ON_CALL(*this, id()).WillByDefault(testing::Invoke([this] {
-            return this->mockSensorId;
-        }));
+        initialize();
     }
 
     static Id makeId(std::string_view service, std::string_view path)
@@ -27,4 +30,12 @@
     const uint64_t mockId = generateUniqueMockId();
 
     Id mockSensorId = Id("SensorMock", "", "");
+
+  private:
+    void initialize()
+    {
+        ON_CALL(*this, id()).WillByDefault(testing::Invoke([this] {
+            return this->mockSensorId;
+        }));
+    }
 };
diff --git a/tests/src/test_metric.cpp b/tests/src/test_metric.cpp
index b40da5a..ff3d120 100644
--- a/tests/src/test_metric.cpp
+++ b/tests/src/test_metric.cpp
@@ -1 +1,115 @@
+#include "helpers/metric_value_helpers.hpp"
+#include "interfaces/sensor.hpp"
 #include "metric.hpp"
+#include "mocks/sensor_mock.hpp"
+#include "printers.hpp"
+#include "utils/conv_container.hpp"
+
+#include <gmock/gmock.h>
+
+using namespace testing;
+
+using Timestamp = uint64_t;
+
+class TestMetric : public Test
+{
+  public:
+    std::vector<std::shared_ptr<SensorMock>> sensorMocks = {
+        std::make_shared<NiceMock<SensorMock>>(),
+        std::make_shared<NiceMock<SensorMock>>(),
+        std::make_shared<NiceMock<SensorMock>>()};
+
+    std::shared_ptr<Metric> sut = std::make_shared<Metric>(
+        utils::convContainer<std::shared_ptr<interfaces::Sensor>>(sensorMocks),
+        "op", "id", "metadata");
+};
+
+TEST_F(TestMetric, subscribesForSensorDuringInitialization)
+{
+    for (auto& sensor : sensorMocks)
+    {
+        EXPECT_CALL(*sensor,
+                    registerForUpdates(Truly([sut = sut.get()](const auto& a0) {
+                        return a0.lock().get() == sut;
+                    })));
+    }
+
+    sut->initialize();
+}
+
+TEST_F(TestMetric, containsNoReadingsWhenNotInitialized)
+{
+    ASSERT_THAT(sut->getReadings(), ElementsAre());
+}
+
+TEST_F(TestMetric, containsEmptyReadingsAfterInitialize)
+{
+    sut->initialize();
+
+    ASSERT_THAT(sut->getReadings(),
+                ElementsAre(MetricValue{"id", "metadata", 0., 0u},
+                            MetricValue{"id", "metadata", 0., 0u},
+                            MetricValue{"id", "metadata", 0., 0u}));
+}
+
+TEST_F(TestMetric, throwsWhenUpdateIsPerformedWhenNotInitialized)
+{
+    EXPECT_THROW(sut->sensorUpdated(*sensorMocks[0], Timestamp{10}),
+                 std::out_of_range);
+    EXPECT_THROW(sut->sensorUpdated(*sensorMocks[1], Timestamp{10}, 20.0),
+                 std::out_of_range);
+}
+
+TEST_F(TestMetric, updatesMetricValuesOnSensorUpdate)
+{
+    sut->initialize();
+
+    sut->sensorUpdated(*sensorMocks[2], Timestamp{18}, 31.0);
+    sut->sensorUpdated(*sensorMocks[0], Timestamp{21});
+
+    ASSERT_THAT(sut->getReadings(),
+                ElementsAre(MetricValue{"id", "metadata", 0., 21u},
+                            MetricValue{"id", "metadata", 0., 0u},
+                            MetricValue{"id", "metadata", 31., 18u}));
+}
+
+TEST_F(TestMetric, throwsWhenUpdateIsPerformedOnUnknownSensor)
+{
+    sut->initialize();
+
+    auto sensor = std::make_shared<StrictMock<SensorMock>>();
+    EXPECT_THROW(sut->sensorUpdated(*sensor, Timestamp{10}), std::out_of_range);
+    EXPECT_THROW(sut->sensorUpdated(*sensor, Timestamp{10}, 20.0),
+                 std::out_of_range);
+}
+
+TEST_F(TestMetric, containsIdInJsonDump)
+{
+    ASSERT_THAT(sut->to_json().at("id"), Eq(nlohmann::json("id")));
+}
+
+TEST_F(TestMetric, containsOpInJsonDump)
+{
+    ASSERT_THAT(sut->to_json().at("operationType"), Eq(nlohmann::json("op")));
+}
+
+TEST_F(TestMetric, containsMetadataInJsonDump)
+{
+    ASSERT_THAT(sut->to_json().at("metricMetadata"),
+                Eq(nlohmann::json("metadata")));
+}
+
+TEST_F(TestMetric, containsSensorPathsInJsonDump)
+{
+    for (size_t i = 0; i < sensorMocks.size(); ++i)
+    {
+        const auto no = std::to_string(i);
+        ON_CALL(*sensorMocks[i], id())
+            .WillByDefault(
+                Return(SensorMock::makeId("service" + no, "path" + no)));
+    }
+
+    ASSERT_THAT(sut->to_json().at("sensorPaths"),
+                Eq(nlohmann::json(
+                    {"service0:path0", "service1:path1", "service2:path2"})));
+}
diff --git a/tests/src/test_report.cpp b/tests/src/test_report.cpp
index 40e85da..ca556b0 100644
--- a/tests/src/test_report.cpp
+++ b/tests/src/test_report.cpp
@@ -477,6 +477,16 @@
     MockFunction<void()> readingsUpdated;
 };
 
+TEST_F(TestReportInitialization, metricsAreInitializedWhenConstructed)
+{
+    for (auto& metric : metricMocks)
+    {
+        EXPECT_CALL(*metric, initialize());
+    }
+
+    sut = makeReport(ReportParams());
+}
+
 TEST_F(TestReportInitialization, readingsPropertiesChangedSingalEmits)
 {
     sut = makeReport(defaultParams.reportingType("Periodic"));
diff --git a/tests/src/test_report_manager.cpp b/tests/src/test_report_manager.cpp
index 813fa19..02bf3ec 100644
--- a/tests/src/test_report_manager.cpp
+++ b/tests/src/test_report_manager.cpp
@@ -2,6 +2,7 @@
 #include "mocks/json_storage_mock.hpp"
 #include "mocks/report_factory_mock.hpp"
 #include "params/report_params.hpp"
+#include "printers.hpp"
 #include "report.hpp"
 #include "report_manager.hpp"
 #include "utils/transform.hpp"
@@ -214,7 +215,7 @@
         ON_CALL(storageMock, list())
             .WillByDefault(Return(std::vector<FilePath>{FilePath("report1")}));
         ON_CALL(storageMock, load(FilePath("report1")))
-            .WillByDefault(Return(data));
+            .WillByDefault(InvokeWithoutArgs([this] { return data; }));
     }
 
     void makeReportManager()
@@ -256,7 +257,6 @@
 {
     data["Version"] = Report::reportVersion - 1;
 
-    ON_CALL(storageMock, load(FilePath("report1"))).WillByDefault(Return(data));
     EXPECT_CALL(storageMock, remove(FilePath("report1")));
 
     makeReportManager();
@@ -267,7 +267,6 @@
 {
     data["Interval"] = "1000";
 
-    ON_CALL(storageMock, load(FilePath("report1"))).WillByDefault(Return(data));
     EXPECT_CALL(storageMock, remove(FilePath("report1")));
 
     makeReportManager();
diff --git a/tests/src/test_sensor.cpp b/tests/src/test_sensor.cpp
index 83151b1..1398738 100644
--- a/tests/src/test_sensor.cpp
+++ b/tests/src/test_sensor.cpp
@@ -1,10 +1,10 @@
 #include "dbus_environment.hpp"
+#include "helpers/sensor_id_helpers.hpp"
 #include "mocks/sensor_listener_mock.hpp"
 #include "printers.hpp"
 #include "sensor.hpp"
 #include "sensor_cache.hpp"
 #include "stubs/dbus_sensor_object.hpp"
-#include "utils/sensor_id_eq.hpp"
 
 #include <sdbusplus/asio/property.hpp>
 
@@ -56,8 +56,8 @@
 TEST_F(TestSensor, createsCorretlyViaSensorCache)
 {
     ASSERT_THAT(sut->id(),
-                sensorIdEq(Sensor::Id("Sensor", DbusEnvironment::serviceName(),
-                                      sensorObject.path())));
+                Eq(Sensor::Id("Sensor", DbusEnvironment::serviceName(),
+                              sensorObject.path())));
 }
 
 TEST_F(TestSensor, notifiesWithValueAfterRegister)
diff --git a/tests/src/test_sensor_cache.cpp b/tests/src/test_sensor_cache.cpp
index cf31add..0db3bc2 100644
--- a/tests/src/test_sensor_cache.cpp
+++ b/tests/src/test_sensor_cache.cpp
@@ -1,7 +1,7 @@
+#include "helpers/sensor_id_helpers.hpp"
 #include "mocks/sensor_mock.hpp"
 #include "printers.hpp"
 #include "sensor_cache.hpp"
-#include "utils/sensor_id_eq.hpp"
 
 #include <initializer_list>
 
@@ -100,5 +100,5 @@
 
     auto expected = SensorMock::makeId("sensor-service", "sensor-path");
 
-    ASSERT_THAT(id, sensorIdEq(expected));
+    ASSERT_THAT(id, Eq(expected));
 }
diff --git a/tests/src/utils/sensor_id_eq.hpp b/tests/src/utils/sensor_id_eq.hpp
deleted file mode 100644
index f952504..0000000
--- a/tests/src/utils/sensor_id_eq.hpp
+++ /dev/null
@@ -1,14 +0,0 @@
-#pragma once
-
-#include "interfaces/sensor.hpp"
-
-#include <gmock/gmock.h>
-
-inline auto sensorIdEq(interfaces::Sensor::Id id)
-{
-    using namespace testing;
-
-    return AllOf(Field(&interfaces::Sensor::Id::type, Eq(id.type)),
-                 Field(&interfaces::Sensor::Id::service, Eq(id.service)),
-                 Field(&interfaces::Sensor::Id::path, Eq(id.path)));
-}