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sauravbhattacharya001sauravbhattacharya001
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test: add comprehensive test suite for ChromaticPolynomialCalculator
26 tests covering: - Empty, single-vertex, and independent-set graphs (base cases) - Complete graphs K2/K3/K4 (falling factorial verification) - Tree polynomials (path and star graphs, k(k-1)^(n-1)) - Cycle polynomials (C4 even, C5 odd — 2-colorability check) - Disconnected components (polynomial product property) - Deletion-contraction on general graphs (diamond, house graph) - PolynomialResult API (degree, coefficients, evaluations, string format) - Second-coefficient = -|E| invariant - Report generation content verification
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‎Gvisual/test/gvisual/ChromaticPolynomialCalculatorTest.java‎

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package gvisual;
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import edu.uci.ics.jung.graph.Graph;
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import edu.uci.ics.jung.graph.UndirectedSparseGraph;
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import org.junit.Before;
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import org.junit.Test;
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import java.util.List;
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import java.util.Map;
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import static org.junit.Assert.*;
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/**
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* Unit tests for {@link ChromaticPolynomialCalculator}.
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*/
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public class ChromaticPolynomialCalculatorTest {
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private Graph<String, String> graph;
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private int edgeId;
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@Before
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public void setUp() {
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graph = new UndirectedSparseGraph<>();
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edgeId = 0;
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}
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private void addEdge(String v1, String v2) {
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if (!graph.containsVertex(v1)) graph.addVertex(v1);
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if (!graph.containsVertex(v2)) graph.addVertex(v2);
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graph.addEdge("e" + edgeId++, v1, v2);
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}
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// --- Empty / trivial graphs ---
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@Test
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public void emptyGraph_polynomialIsOne() {
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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assertEquals(1, r.evaluate(0));
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assertEquals(1, r.evaluate(5));
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assertTrue(r.isExact());
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}
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@Test
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public void singleVertex_polynomialIsK() {
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graph.addVertex("A");
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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// P(G,k) = k
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assertEquals(0, r.evaluate(0));
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assertEquals(1, r.evaluate(1));
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assertEquals(5, r.evaluate(5));
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assertEquals(1, r.getChromaticNumber());
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assertTrue(r.isExact());
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}
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@Test
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public void independentSet_polynomialIsKToN() {
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graph.addVertex("A");
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graph.addVertex("B");
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graph.addVertex("C");
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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// P = k^3
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assertEquals(0, r.evaluate(0));
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assertEquals(1, r.evaluate(1));
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assertEquals(8, r.evaluate(2));
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assertEquals(27, r.evaluate(3));
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assertEquals(1, r.getChromaticNumber());
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}
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@Test(expected = NullPointerException.class)
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public void nullGraph_throws() {
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new ChromaticPolynomialCalculator(null);
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}
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// --- Single edge (K2) ---
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@Test
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public void singleEdge_polynomial() {
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addEdge("A", "B");
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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// P(K2, k) = k(k-1)
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assertEquals(0, r.evaluate(0));
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assertEquals(0, r.evaluate(1));
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assertEquals(2, r.evaluate(2));
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assertEquals(6, r.evaluate(3));
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assertEquals(2, r.getChromaticNumber());
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}
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// --- Complete graphs ---
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@Test
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public void completeK3_polynomial() {
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addEdge("A", "B");
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addEdge("B", "C");
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addEdge("A", "C");
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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// P(K3, k) = k(k-1)(k-2)
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assertEquals(0, r.evaluate(0));
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assertEquals(0, r.evaluate(1));
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assertEquals(0, r.evaluate(2));
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assertEquals(6, r.evaluate(3));
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assertEquals(24, r.evaluate(4));
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assertEquals(3, r.getChromaticNumber());
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assertEquals("Complete K3", r.getSpecialType());
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}
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@Test
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public void completeK4_polynomial() {
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String[] vs = {"A", "B", "C", "D"};
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for (int i = 0; i < vs.length; i++)
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for (int j = i + 1; j < vs.length; j++)
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addEdge(vs[i], vs[j]);
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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// P(K4, k) = k(k-1)(k-2)(k-3)
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assertEquals(0, r.evaluate(3));
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assertEquals(24, r.evaluate(4));
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assertEquals(120, r.evaluate(5));
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assertEquals(4, r.getChromaticNumber());
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}
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// --- Trees ---
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@Test
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public void pathGraph_isTree() {
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// A-B-C-D: tree on 4 vertices
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addEdge("A", "B");
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addEdge("B", "C");
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addEdge("C", "D");
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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// P(T4, k) = k(k-1)^3
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assertEquals(0, r.evaluate(0));
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assertEquals(0, r.evaluate(1));
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assertEquals(2, r.evaluate(2)); // 2*1^3 = 2
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assertEquals(24, r.evaluate(3)); // 3*2^3 = 24
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assertEquals(2, r.getChromaticNumber());
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assertNotNull(r.getSpecialType());
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assertTrue(r.getSpecialType().startsWith("Tree"));
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}
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@Test
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public void starGraph_isTree() {
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// Hub "H" connected to A,B,C,D
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addEdge("H", "A");
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addEdge("H", "B");
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addEdge("H", "C");
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addEdge("H", "D");
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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// P(T5, k) = k(k-1)^4
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assertEquals(0, r.evaluate(1));
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assertEquals(2, r.evaluate(2)); // 2*1 = 2
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assertEquals(48, r.evaluate(3)); // 3*16 = 48
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assertEquals(2, r.getChromaticNumber());
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}
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// --- Cycles ---
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@Test
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public void cycle3_isTriangle() {
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// Same as K3, but test via cycle detection path
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addEdge("A", "B");
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addEdge("B", "C");
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addEdge("A", "C");
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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// K3 is detected as Complete before Cycle, but polynomial is same
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assertEquals(6, r.evaluate(3));
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assertEquals(3, r.getChromaticNumber());
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}
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@Test
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public void cycle4_polynomial() {
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addEdge("A", "B");
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addEdge("B", "C");
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addEdge("C", "D");
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addEdge("D", "A");
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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// P(C4, k) = (k-1)^4 + (k-1)
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// k=2: 1 + 1 = 2
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assertEquals(2, r.evaluate(2));
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// k=3: 16 + 2 = 18
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assertEquals(18, r.evaluate(3));
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assertEquals(2, r.getChromaticNumber());
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assertEquals("Cycle C4", r.getSpecialType());
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}
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@Test
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public void cycle5_oddCycle() {
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addEdge("A", "B");
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addEdge("B", "C");
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addEdge("C", "D");
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addEdge("D", "E");
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addEdge("E", "A");
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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// P(C5, k) = (k-1)^5 - (k-1)
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// k=2: 1 - 1 = 0 (odd cycle is not 2-colorable)
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assertEquals(0, r.evaluate(2));
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// k=3: 32 - 2 = 30
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assertEquals(30, r.evaluate(3));
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assertEquals(3, r.getChromaticNumber());
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}
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// --- Disconnected components ---
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@Test
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public void disconnectedGraph_productsPolynomials() {
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// K2 + isolated vertex = P(K2,k) * P(v,k) = k(k-1) * k = k^2(k-1)
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addEdge("A", "B");
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graph.addVertex("C");
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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assertEquals(0, r.evaluate(0));
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assertEquals(0, r.evaluate(1));
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// k^2*(k-1) at k=2 = 4*1 = 4
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assertEquals(4, r.evaluate(2));
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assertEquals(18, r.evaluate(3)); // 9*2 = 18
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}
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@Test
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public void twoDisconnectedEdges() {
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// K2 + K2 = [k(k-1)]^2
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addEdge("A", "B");
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addEdge("C", "D");
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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// k=2: [2*1]^2 = 4
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assertEquals(4, r.evaluate(2));
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// k=3: [3*2]^2 = 36
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assertEquals(36, r.evaluate(3));
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}
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// --- Deletion-contraction (general graph) ---
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@Test
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public void diamondGraph_deletionContraction() {
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// Diamond: K4 minus one edge
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addEdge("A", "B");
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addEdge("A", "C");
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addEdge("A", "D");
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addEdge("B", "C");
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addEdge("C", "D");
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// Missing B-D
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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// Chromatic number should be 3 (triangle A-B-C exists)
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assertEquals(3, r.getChromaticNumber());
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assertEquals(0, r.evaluate(2));
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assertTrue(r.evaluate(3) > 0);
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assertTrue(r.isExact());
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}
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@Test
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public void petersenLikeSmall_exact() {
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// A small non-trivial graph: house graph (square + triangle on top)
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// A-B-C-D-A plus B-E and C-E
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addEdge("A", "B");
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addEdge("B", "C");
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addEdge("C", "D");
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addEdge("D", "A");
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addEdge("B", "E");
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addEdge("C", "E");
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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assertTrue(r.isExact());
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assertEquals(3, r.getChromaticNumber());
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// P(G,0) must always be 0 for non-empty graphs
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assertEquals(0, r.evaluate(0));
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}
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// --- PolynomialResult API ---
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@Test
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public void resultDegreeEqualsVertexCount() {
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addEdge("A", "B");
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addEdge("B", "C");
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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assertEquals(r.getVertexCount(), r.getDegree());
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}
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@Test
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public void polynomialStringNotEmpty() {
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addEdge("A", "B");
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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assertFalse(r.getPolynomialString().isEmpty());
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}
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@Test
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public void evaluationsListPopulated() {
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addEdge("A", "B");
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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assertFalse(r.getEvaluations().isEmpty());
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// First entry k=0 should always be 0 for non-empty graph
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assertEquals(Integer.valueOf(0), r.getEvaluations().get(0).getKey());
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assertEquals(Long.valueOf(0), r.getEvaluations().get(0).getValue());
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}
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@Test
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public void coefficientSecondTermEqualsNegativeEdgeCount() {
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// For any simple graph, coefficient of k^(n-1) = -|E|
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addEdge("A", "B");
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addEdge("B", "C");
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addEdge("A", "C");
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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ChromaticPolynomialCalculator.PolynomialResult r = calc.compute();
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long[] coeffs = r.getCoefficients();
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// Leading: coeffs[n] = 1, second: coeffs[n-1] = -|E|
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assertEquals(1, coeffs[coeffs.length - 1]);
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assertEquals(-r.getEdgeCount(), coeffs[coeffs.length - 2]);
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}
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// --- Report generation ---
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@Test
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public void reportNotEmpty() {
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addEdge("A", "B");
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addEdge("B", "C");
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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String report = calc.generateReport();
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assertNotNull(report);
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assertTrue(report.contains("CHROMATIC POLYNOMIAL"));
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assertTrue(report.contains("Chromatic number"));
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}
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@Test
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public void reportIncludesSpecialType() {
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// K3
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addEdge("A", "B");
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addEdge("B", "C");
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addEdge("A", "C");
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ChromaticPolynomialCalculator calc = new ChromaticPolynomialCalculator(graph);
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String report = calc.generateReport();
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assertTrue(report.contains("Complete K3"));
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}
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}

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