Towards/modules/metrics/tests/MetricSeriesTests.cpp

#include "metrics/MetricSeries.hpp"

#include "catch2/catch_test_macros.hpp"

#include <chrono>

using namespace std::chrono_literals;

using tw::metrics::MetricField;
using tw::metrics::MetricSeries;

using Clock  = std::chrono::steady_clock;
using Series = MetricSeries<std::chrono::seconds>;

/** Fixed origin so every test drives the series by hand. */
static Clock::time_point at(int64_t seconds) {
    return Clock::time_point{} + std::chrono::hours(1) + std::chrono::seconds(seconds);
}

TEST_CASE("Series starts empty", "[metric_series]") {
    Series series(8);

    REQUIRE(series.capacity() == 8);
    REQUIRE(series.size() == 0);
    REQUIRE(series.is_empty());
    REQUIRE(series.window().is_empty());
}

TEST_CASE("Series rejects a zero capacity", "[metric_series]") {
    REQUIRE_THROWS_AS(Series(0), std::invalid_argument);
}

TEST_CASE("Values in the same interval fold into one bucket", "[metric_series]") {
    Series series(8);

    series.push(1.0, at(0));
    series.push(3.0, at(0));

    REQUIRE(series.size() == 1);
    REQUIRE(series.at_age(0).count == 2);
    REQUIRE(series.at_age(0).avg() == 2.0);
    REQUIRE(series.at_age(0).min == 1.0);
    REQUIRE(series.at_age(0).max == 3.0);
}

TEST_CASE("Values in different intervals land in different buckets", "[metric_series]") {
    Series series(8);

    series.push(1.0, at(0));
    series.push(5.0, at(1));

    REQUIRE(series.size() == 2);
    REQUIRE(series.at_age(0).sum == 5.0);
    REQUIRE(series.at_age(1).sum == 1.0);
}

TEST_CASE("Intervals without a value become empty buckets", "[metric_series]") {
    Series series(8);

    series.push(1.0, at(0));
    series.push(4.0, at(3));

    REQUIRE(series.size() == 4);
    REQUIRE(series.at_age(0).sum == 4.0);
    REQUIRE(series.at_age(1).is_empty());
    REQUIRE(series.at_age(2).is_empty());
    REQUIRE(series.at_age(3).sum == 1.0);
}

TEST_CASE("Series never holds more than its capacity", "[metric_series]") {
    Series series(4);

    for(int64_t i = 0; i < 10; i++) {
        series.push((double)i, at(i));
    }

    REQUIRE(series.size() == 4);
    REQUIRE(series.at_age(0).sum == 9.0);
    REQUIRE(series.at_age(3).sum == 6.0);
}

TEST_CASE("A gap wider than the ring leaves only the newest bucket filled", "[metric_series]") {
    Series series(4);

    series.push(1.0, at(0));
    series.push(2.0, at(100));

    REQUIRE(series.size() == 4);
    REQUIRE(series.at_age(0).sum == 2.0);
    REQUIRE(series.at_age(1).is_empty());
    REQUIRE(series.at_age(2).is_empty());
    REQUIRE(series.at_age(3).is_empty());
}

TEST_CASE("Buckets dropped by wrapping do not come back", "[metric_series]") {
    Series series(4);

    series.push(100.0, at(0));

    for(int64_t i = 1; i < 5; i++) {
        series.push(1.0, at(i));
    }

    REQUIRE(series.window().max == 1.0);
}

TEST_CASE("Window aggregates across buckets", "[metric_series]") {
    Series series(8);

    series.push(4.0, at(0));
    series.push(1.0, at(1));
    series.push(7.0, at(2));

    auto window = series.window();

    REQUIRE(window.count == 3);
    REQUIRE(window.sum == 12.0);
    REQUIRE(window.min == 1.0);
    REQUIRE(window.max == 7.0);
    REQUIRE(window.avg() == 4.0);
}

TEST_CASE("Window can be narrowed to the newest buckets", "[metric_series]") {
    Series series(8);

    series.push(4.0, at(0));
    series.push(1.0, at(1));
    series.push(7.0, at(2));

    auto window = series.window(2);

    REQUIRE(window.count == 2);
    REQUIRE(window.min == 1.0);
    REQUIRE(window.max == 7.0);
}

TEST_CASE("Empty buckets do not skew the window extremes", "[metric_series]") {
    Series series(8);

    series.push(5.0, at(0));
    series.push(9.0, at(4));

    auto window = series.window();

    REQUIRE(window.count == 2);
    REQUIRE(window.min == 5.0);
    REQUIRE(window.max == 9.0);
}

TEST_CASE("A late value folds into the bucket it belongs to", "[metric_series]") {
    Series series(8);

    series.push(1.0, at(0));
    series.push(2.0, at(2));
    series.push(6.0, at(1));

    REQUIRE(series.size() == 3);
    REQUIRE(series.at_age(1).sum == 6.0);
    REQUIRE(series.at_age(0).sum == 2.0);
}

TEST_CASE("A value older than every bucket held is dropped", "[metric_series]") {
    Series series(4);

    for(int64_t i = 0; i < 4; i++) {
        series.push(1.0, at(i));
    }

    series.push(99.0, at(-10));

    REQUIRE(series.size() == 4);
    REQUIRE(series.window().max == 1.0);
    REQUIRE(series.window().count == 4);
}

TEST_CASE("Linearize writes buckets oldest first", "[metric_series]") {
    Series series(8);

    series.push(1.0, at(0));
    series.push(2.0, at(1));
    series.push(3.0, at(2));

    std::vector<double> xs;
    std::vector<double> ys;

    size_t count = series.linearize(xs, ys, MetricField::Sum);

    REQUIRE(count == 3);
    REQUIRE(xs == std::vector<double>{-2.0, -1.0, 0.0});
    REQUIRE(ys == std::vector<double>{1.0, 2.0, 3.0});
}

TEST_CASE("Linearize can be limited to the newest buckets", "[metric_series]") {
    Series series(8);

    series.push(1.0, at(0));
    series.push(2.0, at(1));
    series.push(3.0, at(2));

    std::vector<double> xs;
    std::vector<double> ys;

    size_t count = series.linearize(xs, ys, MetricField::Sum, 2);

    REQUIRE(count == 2);
    REQUIRE(xs == std::vector<double>{-1.0, 0.0});
    REQUIRE(ys == std::vector<double>{2.0, 3.0});
}

TEST_CASE("Linearize can leave out the newest buckets", "[metric_series]") {
    Series series(8);

    series.push(1.0, at(0));
    series.push(2.0, at(1));
    series.push(3.0, at(2));

    std::vector<double> xs;
    std::vector<double> ys;

    size_t count = series.linearize(xs, ys, MetricField::Sum, 8, 1);

    REQUIRE(count == 2);
    REQUIRE(ys == std::vector<double>{1.0, 2.0});
}

TEST_CASE("Skipping the newest bucket keeps the ages of the rest", "[metric_series]") {
    Series series(8);

    series.push(1.0, at(0));
    series.push(2.0, at(1));
    series.push(3.0, at(2));

    std::vector<double> xs;
    std::vector<double> ys;

    series.linearize(xs, ys, MetricField::Sum, 8, 1);

    REQUIRE(xs == std::vector<double>{-2.0, -1.0});
}

TEST_CASE("Skipping more buckets than are held writes nothing", "[metric_series]") {
    Series series(8);

    series.push(1.0, at(0));

    std::vector<double> xs;
    std::vector<double> ys;

    size_t count = series.linearize(xs, ys, MetricField::Sum, 8, 4);

    REQUIRE(count == 0);
    REQUIRE(xs.empty());
    REQUIRE(ys.empty());
}

TEST_CASE("A limit counts buckets that were not skipped", "[metric_series]") {
    Series series(8);

    for(int64_t i = 0; i < 5; i++) {
        series.push((double)i, at(i));
    }

    std::vector<double> xs;
    std::vector<double> ys;

    size_t count = series.linearize(xs, ys, MetricField::Sum, 2, 1);

    REQUIRE(count == 2);
    REQUIRE(ys == std::vector<double>{2.0, 3.0});
}

TEST_CASE("Linearize reports empty buckets as zero", "[metric_series]") {
    Series series(8);

    series.push(5.0, at(0));
    series.push(9.0, at(2));

    std::vector<double> xs;
    std::vector<double> ys;

    series.linearize(xs, ys, MetricField::Max);

    REQUIRE(ys == std::vector<double>{5.0, 0.0, 9.0});
}

TEST_CASE("Linearize resizes the vectors it is given", "[metric_series]") {
    Series series(8);

    series.push(1.0, at(0));

    std::vector<double> xs(64, 7.0);
    std::vector<double> ys(64, 7.0);

    series.linearize(xs, ys, MetricField::Avg);

    REQUIRE(xs.size() == 1);
    REQUIRE(ys.size() == 1);
}

TEST_CASE("Clear empties the series but keeps its capacity", "[metric_series]") {
    Series series(8);

    series.push(1.0, at(0));
    series.clear();

    REQUIRE(series.is_empty());
    REQUIRE(series.capacity() == 8);

    series.push(2.0, at(1));

    REQUIRE(series.size() == 1);
    REQUIRE(series.at_age(0).sum == 2.0);
}

TEST_CASE("A coarser interval folds more values together", "[metric_series]") {
    MetricSeries<std::chrono::minutes> series(4);

    series.push(1.0, at(0));
    series.push(2.0, at(30));
    series.push(3.0, at(90));

    REQUIRE(series.size() == 2);
    REQUIRE(series.at_age(1).count == 2);
    REQUIRE(series.at_age(0).sum == 3.0);
}