Add tests for Solution. Fix couple of issues with loop ranges

src/main/java/by/andd3dfx/math/pde/solver/Solution.java

@@ -20,7 +20,7 @@ public void sUt(String fileName, double[] t) {
         }
 
         var sb = new StringBuilder();
-        for (var i = 0; i <= area.x().n(); i++) {
+        for (var i = 0; i < area.x().n(); i++) {
             sb.append(area.x().x(i));
             for (var t_i : t) {
                 sb.append(" ").append(solution.get(area.t().i(t_i), i));
@@ -53,7 +53,7 @@ public void sUx(String fileName, double[] x) {
         }
 
         var sb = new StringBuilder();
-        for (int i = 0; i <= area.t().n(); i++) {
+        for (int i = 0; i < area.t().n(); i++) {
             sb.append(area.t().x(i));
             for (var x_i : x) {
                 sb.append(" ").append(solution.get(i, area.x().i(x_i)));
@@ -124,7 +124,7 @@ public Matrix gUx(int ix) {
 
         int M = solution.getM();
         var matrix = new Matrix(2, M);
-        for (int i = 0; i <= M; i++) {
+        for (int i = 0; i < M; i++) {
             matrix.setX(i, area.t().x(i));
             matrix.setY(i, solution.get(i, ix));
         }

src/test/java/by/andd3dfx/math/pde/solver/SolutionTest.java

@@ -0,0 +1,195 @@
+package by.andd3dfx.math.pde.solver;
+
+import by.andd3dfx.math.Area;
+import by.andd3dfx.math.Interval;
+import by.andd3dfx.math.Matrix;
+import by.andd3dfx.math.pde.equation.Equation;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+
+import static by.andd3dfx.util.FileComparisonHelper.BUILD_PATH;
+import static by.andd3dfx.util.FileComparisonHelper.checkGeneratedFileContent;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+class SolutionTest {
+
+    @Test
+    void sUtForArray() throws IOException {
+        var fileName = "sUt-array.txt";
+        var solution = buildSolution();
+
+        solution.sUt(BUILD_PATH + fileName, new double[]{2.5, 5.0});
+
+        checkGeneratedFileContent(fileName);
+    }
+
+    @Test
+    void sUtForArrayWithWrongParam() {
+        var solution = buildSolution();
+
+        assertThrows(AssertionError.class, () ->
+                solution.sUt(BUILD_PATH + "sUt-arr.txt", new double[]{1.0, 2.5}));
+        assertThrows(AssertionError.class, () ->
+                solution.sUt(BUILD_PATH + "sUt-arr.txt", new double[]{2.5, 2.6, 6.5}));
+    }
+
+    @Test
+    void sUt() throws IOException {
+        var fileName = "sUt.txt";
+        var solution = buildSolution();
+
+        solution.sUt(BUILD_PATH + fileName, 5.0);
+
+        checkGeneratedFileContent(fileName);
+    }
+
+    @Test
+    void sUtWithWrongParam() {
+        var solution = buildSolution();
+
+        assertThrows(AssertionError.class, () -> solution.sUt(BUILD_PATH + "sUt.txt", 1.0));
+        assertThrows(AssertionError.class, () -> solution.sUt(BUILD_PATH + "sUt.txt", 6.5));
+    }
+
+    @Test
+    void sUxForArray() throws IOException {
+        var fileName = "sUx-array.txt";
+        var solution = buildSolution();
+
+        solution.sUx(BUILD_PATH + fileName, new double[]{11.0, 12.0});
+
+        checkGeneratedFileContent(fileName);
+    }
+
+    @Test
+    void sUxForArrayWithWrongParam() {
+        var solution = buildSolution();
+
+        assertThrows(AssertionError.class, () ->
+                solution.sUx(BUILD_PATH + "sUx-arr.txt", new double[]{9.0, 11.0}));
+        assertThrows(AssertionError.class, () ->
+                solution.sUx(BUILD_PATH + "sUx-arr.txt", new double[]{10.0, 12.5, 13.5}));
+    }
+
+    @Test
+    void sUx() throws IOException {
+        var fileName = "sUx.txt";
+        var solution = buildSolution();
+
+        solution.sUx(BUILD_PATH + fileName, 12.0);
+
+        checkGeneratedFileContent(fileName);
+    }
+
+    @Test
+    void sUxWithWrongParam() {
+        var solution = buildSolution();
+
+        assertThrows(AssertionError.class, () -> solution.sUx(BUILD_PATH + "sUx.txt", 9.0));
+        assertThrows(AssertionError.class, () -> solution.sUx(BUILD_PATH + "sUx.txt", 13.5));
+    }
+
+    @Test
+    void gUtForDouble() {
+        var solution = buildSolution();
+
+        var result = solution.gUt(5.0);
+
+        checkUtAssertions(result);
+    }
+
+    @Test
+    void gUtForInt() {
+        var solution = buildSolution();
+
+        var result = solution.gUt(2);
+
+        checkUtAssertions(result);
+    }
+
+    @Test
+    void gUtForIntWithWrongParam() {
+        var solution = buildSolution();
+
+        assertThrows(AssertionError.class, () -> solution.gUt(-1));
+        assertThrows(AssertionError.class, () -> solution.gUt(solution.solution().getM()));
+    }
+
+    @Test
+    void gUxForDouble() {
+        var solution = buildSolution();
+
+        var result = solution.gUx(10 + 3 / 4.);
+
+        checkUxAssertions(result);
+    }
+
+    @Test
+    void gUxForInt() {
+        var solution = buildSolution();
+
+        var result = solution.gUx(1);
+
+        checkUxAssertions(result);
+    }
+
+    @Test
+    void gUxForIntWithWrongParam() {
+        var solution = buildSolution();
+
+        assertThrows(AssertionError.class, () -> solution.gUx(-1));
+        assertThrows(AssertionError.class, () -> solution.gUx(solution.solution().getN()));
+    }
+
+    /**
+     * <pre>
+     * Build solution for
+     * - space interval [10,13] with 3 steps &
+     * - time interval [2,6] with 2 steps
+     * - matrix:
+     *   [[50,80,90,99],
+     *    [30,70,120,125],
+     *    [45,56,78,786]]
+     * </pre>
+     */
+    private Solution<Equation> buildSolution() {
+        var spaceSteps = 4;
+        var timeSteps = 3;
+
+        var solutionMatrix = new Matrix(timeSteps, spaceSteps);
+        solutionMatrix.set(0, new double[]{50, 80, 90, 99});
+        solutionMatrix.set(1, new double[]{30, 70, 120, 125});
+        solutionMatrix.set(2, new double[]{45, 56, 78, 786});
+
+        return new Solution<>(null, new Area(
+                new Interval(10, 13, spaceSteps),
+                new Interval(2, 6, timeSteps)
+        ), solutionMatrix);
+    }
+
+    private static void checkUtAssertions(Matrix result) {
+        assertThat(result.getM()).isEqualTo(2);
+        assertThat(result.getN()).isEqualTo(4);
+        assertThat(result.x(0)).isEqualTo(10);
+        assertThat(result.x(1)).isEqualTo(10 + 3 / 4.);
+        assertThat(result.x(2)).isEqualTo(10 + 6 / 4.);
+        assertThat(result.x(3)).isEqualTo(10 + 9 / 4.);
+        assertThat(result.y(0)).isEqualTo(45);
+        assertThat(result.y(1)).isEqualTo(56);
+        assertThat(result.y(2)).isEqualTo(78);
+        assertThat(result.y(3)).isEqualTo(786);
+    }
+
+    private static void checkUxAssertions(Matrix result) {
+        assertThat(result.getM()).isEqualTo(2);
+        assertThat(result.getN()).isEqualTo(3);
+        assertThat(result.x(0)).isEqualTo(2);
+        assertThat(result.x(1)).isEqualTo(2 + 4 / 3.);
+        assertThat(result.x(2)).isEqualTo(2 + 8 / 3.);
+        assertThat(result.y(0)).isEqualTo(80);
+        assertThat(result.y(1)).isEqualTo(70);
+        assertThat(result.y(2)).isEqualTo(56);
+    }
+}

src/test/resources/sUt-array.txt

@@ -0,0 +1,4 @@
+10.0 50.0 45.0
+10.75 80.0 56.0
+11.5 90.0 78.0
+12.25 99.0 786.0

src/test/resources/sUt.txt

@@ -0,0 +1,4 @@
+10.0 45.0
+10.75 56.0
+11.5 78.0
+12.25 786.0

src/test/resources/sUx-array.txt

@@ -0,0 +1,3 @@
+2.0 80.0 90.0
+3.333333333333333 70.0 120.0
+4.666666666666666 56.0 78.0

src/test/resources/sUx.txt

@@ -0,0 +1,3 @@
+2.0 90.0
+3.333333333333333 120.0
+4.666666666666666 78.0