src/test/java/com/montecarlo/tests/ArcTest.java - master - shvidkuli/kkrjava

src/test/java/com/montecarlo/tests/ArcTest.java
174 строки6 KB
kroc400
first_commit
30 апр 2026, 22:44
30 апр 2026, 22:442347fdb
package com.montecarlo.tests;

import com.montecarlo.geometry.Arc;
import com.montecarlo.geometry.BoundingBox;
import com.montecarlo.geometry.Point;
import org.junit.Test;

import static org.junit.Assert.*;

/**
 * Unit tests for {@link Arc} (semicircle / half-disk).
 *
 * <p>Default semicircle used in figure "debf":
 * <pre>
 *   Diameter endpoints: F = (2, 0), E = (4, 2)
 *   Centre = (3, 1),  radius = √2
 *   Inward normal points towards D = (0, 4)
 *   → normal direction ≈ (−1/√2, 1/√2)
 *   → A point (x,y) is inside iff (x−3)²+(y−1)² ≤ 2  AND  y−x+2 ≥ 0
 *   Area = π·(√2)²/2 = π
 * </pre>
 * </p>
 */
public class ArcTest {

    private static final double SQRT2 = Math.sqrt(2.0);

    // Default semicircle: centre=(3,1), r=√2, reference point D=(0,4)
    private static final Arc SEMI = new Arc(
        new Point(3, 1),
        SQRT2,
        new Point(0, 4)   // D — reference on the filled side
    );

    // -----------------------------------------------------------------------
    // Area
    // -----------------------------------------------------------------------

    @Test
    public void testArea() {
        assertEquals("Area of default semicircle must be π", Math.PI, SEMI.analyticalArea(), 1e-12);
    }

    @Test
    public void testAreaUnitSemicircle() {
        Arc unit = new Arc(new Point(0, 0), 1.0, new Point(0, 1));
        assertEquals(Math.PI / 2, unit.analyticalArea(), 1e-12);
    }

    // -----------------------------------------------------------------------
    // contains — diameter endpoints (on boundary)
    // -----------------------------------------------------------------------

    @Test
    public void testContainsDiameterEndpointF() {
        // F = (2, 0): on the arc boundary
        assertTrue(SEMI.contains(new Point(2, 0)));
    }

    @Test
    public void testContainsDiameterEndpointE() {
        // E = (4, 2): on the arc boundary
        assertTrue(SEMI.contains(new Point(4, 2)));
    }

    // -----------------------------------------------------------------------
    // contains — centre (on diameter chord → boundary)
    // -----------------------------------------------------------------------

    @Test
    public void testContainsCentre() {
        // Centre (3,1): on the diameter chord, distance = 0
        assertTrue(SEMI.contains(new Point(3, 1)));
    }

    // -----------------------------------------------------------------------
    // contains — points strictly inside
    // -----------------------------------------------------------------------

    @Test
    public void testContainsInteriorPoint() {
        // (2, 2): dist from (3,1) = √2, on D-side: 2−2+2=2 ≥ 0 → inside (on arc)
        assertTrue(SEMI.contains(new Point(2, 2)));
    }

    @Test
    public void testContainsInteriorCenter() {
        // (2.5, 1.5): dist² = 0.25+0.25=0.5 < 2; D-side: 1.5−2.5+2=1 ≥ 0 → inside
        assertTrue(SEMI.contains(new Point(2.5, 1.5)));
    }

    @Test
    public void testContainsTopCardinal() {
        // Top of circle: (3, 1+√2) — should be on D-side (y−x+2 = √2 ≥ 0)
        assertTrue(SEMI.contains(new Point(3, 1 + SQRT2)));
    }

    @Test
    public void testContainsLeftCardinal() {
        // Left of circle: (3−√2, 1) — should be on D-side
        assertTrue(SEMI.contains(new Point(3 - SQRT2, 1)));
    }

    // -----------------------------------------------------------------------
    // contains — points outside
    // -----------------------------------------------------------------------

    @Test
    public void testNotContainsB() {
        // B = (4, 0): on arc of circle but on the WRONG (B) side: 0−4+2=−2 < 0
        assertFalse(SEMI.contains(new Point(4, 0)));
    }

    @Test
    public void testNotContainsRightCardinal() {
        // Right of circle (3+√2, 1): B-side
        assertFalse(SEMI.contains(new Point(3 + SQRT2, 1)));
    }

    @Test
    public void testNotContainsBottomCardinal() {
        // Bottom of circle (3, 1−√2): B-side
        assertFalse(SEMI.contains(new Point(3, 1 - SQRT2)));
    }

    @Test
    public void testNotContainsFarAwayPoint() {
        assertFalse(SEMI.contains(new Point(10, 10)));
    }

    @Test
    public void testNotContainsOrigin() {
        // (0,0): distance from centre = √(9+1) = √10 >> √2
        assertFalse(SEMI.contains(new Point(0, 0)));
    }

    // -----------------------------------------------------------------------
    // Bounding box
    // -----------------------------------------------------------------------

    @Test
    public void testBoundingBoxMinX() {
        // Leftmost: 3 − √2 ≈ 1.586
        assertEquals(3 - SQRT2, SEMI.getBoundingBox().getMinX(), 1e-10);
    }

    @Test
    public void testBoundingBoxMinY() {
        // Bottommost D-side point: min(ep1.y, ep2.y) = min(2, 0) = 0
        assertEquals(0.0, SEMI.getBoundingBox().getMinY(), 1e-10);
    }

    @Test
    public void testBoundingBoxMaxX() {
        // Rightmost D-side point: max(ep1.x, ep2.x) = max(4, 2) = 4
        assertEquals(4.0, SEMI.getBoundingBox().getMaxX(), 1e-10);
    }

    @Test
    public void testBoundingBoxMaxY() {
        // Topmost: 1 + √2 ≈ 2.414
        assertEquals(1 + SQRT2, SEMI.getBoundingBox().getMaxY(), 1e-10);
    }

    // -----------------------------------------------------------------------
    // Constructor guard
    // -----------------------------------------------------------------------

    @Test(expected = IllegalArgumentException.class)
    public void testConstructorRefPointAtCentre() {
        // refPoint == centre should throw
        new Arc(new Point(0, 0), 1.0, new Point(0, 0));
    }
}