sns: moving average should be an average

ref. #2543

code/espurna/filters/MovingAverageFilter.h

@@ -12,9 +12,9 @@
 class MovingAverageFilter : public BaseFilter {
 public:
     void update(double value) override {
-        _sum = _sum + value - _values[_sample];
-        _values[_sample] = value;
-        _sample = (_sample + 1) % _values.capacity();
+        if (_values.size() < _values.capacity()) {
+            _values.push_back(value);
+        }
     }
 
     size_t capacity() const override {
@@ -22,18 +22,28 @@ public:
     }
 
     double value() const override {
-        return _sum;
+        double out{ 0. };
+
+        for (const auto& value : _values) {
+            out += value;
+        }
+
+        if (_values.size()) {
+            out /= _values.size();
+        }
+
+        return out;
     }
 
     void resize(size_t size) override {
-        _sum = 0.0;
-        _sample = 0;
         _values.clear();
-        _values.resize(size, 0.0);
+        _values.reserve(size);
+    }
+
+    void reset() override {
+        _values.clear();
     }
 
 private:
-    std::vector<double> _values {{0.0}};
-    size_t _sample = 0;
-    double _sum = 0;
+    std::vector<double> _values{};
 };

code/test/unit/src/filters/filters.cpp

@@ -94,7 +94,22 @@ void test_median() {
 }
 
 void test_moving_average() {
-    // TODO
+    auto filter = MovingAverageFilter();
+
+    TEST_ASSERT_EQUAL(0, filter.capacity());
+    TEST_ASSERT_EQUAL_DOUBLE(0.0, filter.value());
+
+    const double samples[] {22., 22.3, 22.1, 22.1, 22.1, 22.0, 22.5, 22.1};
+    filter.resize(std::size(samples));
+
+    TEST_ASSERT_EQUAL(std::size(samples), filter.capacity());
+    TEST_ASSERT_EQUAL_DOUBLE(0.0, filter.value());
+
+    for (const auto& sample : samples) {
+        filter.update(sample);
+    }
+
+    TEST_ASSERT_EQUAL_DOUBLE(22.15, filter.value());
 }
 
 void test_sum() {