test_AlphaFilter.cpp

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#include <gtest/gtest.h>
#include <cmath>
#include <matrix/math.hpp>

#include "EKF/AlphaFilter.hpp"

using matrix::Vector3f;

class AlphaFilterTest : public ::testing::Test {
 public:
    AlphaFilter<float> filter_float{};
    AlphaFilter<Vector3f> filter_v3{};
};

TEST_F(AlphaFilterTest, initializeToZero)
{
    ASSERT_EQ(filter_float.getState(), 0.f);
}

TEST_F(AlphaFilterTest, resetToValue)
{
    const float reset_value = 42.42f;
    filter_float.reset(reset_value);
    ASSERT_EQ(filter_float.getState(), reset_value);
}

TEST_F(AlphaFilterTest, runZero)
{
    const float input = 0.f;
    for (int i = 0; i < 10; i++) {
        filter_float.update(input);
    }
    ASSERT_EQ(filter_float.getState(), input);
}

TEST_F(AlphaFilterTest, runPositive)
{
    // GIVEN an input of 1 in a filter with a default time constant of 9 (alpha = 0.1)
    const float input = 1.f;

    // WHEN we run the filter 9 times
    for (int i = 0; i < 9; i++) {
        filter_float.update(input);
    }

    // THEN the state of the filter should have reached 63%
    ASSERT_NEAR(filter_float.getState(), 0.63f, 0.02);
}

TEST_F(AlphaFilterTest, runNegative)
{
    // GIVEN an input of 1 in a filter with a default time constant of 9 (alpha = 0.1)
    const float input = -1.f;

    // WHEN we run the filter 9 times
    for (int i = 0; i < 9; i++) {
        filter_float.update(input);
    }

    // THEN the state of the filter should have reached 63%
    ASSERT_NEAR(filter_float.getState(), -0.63f, 0.02);
}

TEST_F(AlphaFilterTest, riseTime)
{
    // GIVEN an input of 1 in a filter with a default time constant of 9 (alpha = 0.1)
    const float input = 1.f;

    // WHEN we run the filter 27 times (3 * time constant)
    for (int i = 0; i < 3 * 9; i++) {
        filter_float.update(input);
    }

    // THEN the state of the filter should have reached 95%
    ASSERT_NEAR(filter_float.getState(), 0.95f, 0.02f);
}

TEST_F(AlphaFilterTest, convergence)
{
    // GIVEN an input of 1 in a filter with a default time constant of 9 (alpha = 0.1)
    const float input = 1.f;

    // WHEN we run the filter 45 times (5 * time constant)
    for (int i = 0; i < 5 * 9; i++) {
        filter_float.update(input);
    }

    // THEN the state of the filter should have converged to the input
    ASSERT_NEAR(filter_float.getState(), 1.f, 0.01f);
}

TEST_F(AlphaFilterTest, convergenceVector3f)
{
    // GIVEN an Vector3f input in a filter with a default time constant of 9 (alpha = 0.1)
    const Vector3f input = {3.f, 7.f, -11.f};

    // WHEN we run the filter 45 times (5 * time constant)
    for (int i = 0; i < 5 * 9; i++) {
        filter_v3.update(input);
    }

    // THEN the state of the filter should have converged to the input (1% error allowed)
    Vector3f output = filter_v3.getState();
    for (int i = 0; i < 3; i++) {
        ASSERT_NEAR(output(i), input(i), fabsf(0.01f * input(i)));
    }
}

TEST_F(AlphaFilterTest, convergenceVector3fAlpha)
{
    // GIVEN a Vector3f input in a filter with a defined time constant and the default sampling time
    const Vector3f input = {3.f, 7.f, -11.f};
    const float tau = 18.f;
    const float dt = 1.f;
    const float alpha = dt / tau;

    // WHEN we run the filter 18 times (1 * time constant)
    for (int i = 0; i < 18; i++) {
        filter_v3.update(input, alpha); // dt is assumed equal to 1
    }

    // THEN the state of the filter should have reached 65% (2% error allowed)
    Vector3f output = filter_v3.getState();
    for (int i = 0; i < 3; i++) {
        ASSERT_NEAR(output(i), 0.63f * input(i), fabsf(0.02f * input(i)));
    }
}

TEST_F(AlphaFilterTest, convergenceVector3fTauDt)
{
    // GIVEN a Vector3f input in a filter with a defined time constant and sampling time
    const Vector3f input = {51.f, 7.f, -11.f};
    const float tau = 2.f;
    const float dt = 0.1f;

    // WHEN we run the filter (1 * time constant)
    const float n = tau / dt;
    for (int i = 0; i < n; i++) {
        filter_v3.update(input, tau, dt);
    }

    // THEN the state of the filter should have reached 65% (2% error allowed)
    Vector3f output = filter_v3.getState();
    for (int i = 0; i < 3; i++) {
        ASSERT_NEAR(output(i), 0.63f * input(i), fabsf(0.02f * input(i)));
    }

    // ALSO when the filter is reset to a specified value
    const Vector3f reset_vector = {-1.f, 71.f, -42.f};
    filter_v3.reset(reset_vector);
    output = filter_v3.getState();

    // THEN the filter should exactly contain those values
    for (int i = 0; i < 3; i++) {
        ASSERT_EQ(output(i), reset_vector(i));
    }
}