Ajout test

src/main/java/formula/Constant.java

+package formula;
+
+import java.util.HashMap;
+
+public class Constant implements Formula {
+
+  private double value;
+
+  public Constant(double value) {
+    // TODO : change the code.
+  }
+
+  /**
+   * Compute the value of the formula
+   *
+   * @param xValue the value of the variable x
+   * @return the value of the function when the variable x has value {@code xValue}
+   */
+  @Override
+  public double eval(double xValue) {
+    // TODO : change the code.
+    return 0;
+  }
+
+  /**
+   * Compute the derivative of the formula.
+   *
+   * @return the derivative of the formula
+   */
+  @Override
+  public Formula derivative() {
+    // TODO : change the code.
+    return this;
+  }
+
+  /**
+   * Return a {@code String} representation of the formula.
+   *
+   * @return the formula as a {@code String}
+   */
+  @Override
+  public String toString() {
+    // TODO : change the code.
+    return "toto";
+  }
+
+  /**
+   * Indicates whether some other object is "equal to" this one.
+   *
+   * @param obj the reference object with which to compare.
+   * @return {@code true} if this object is the same as the obj
+   * argument; {@code false} otherwise.
+   * @see #hashCode()
+   * @see HashMap
+   */
+  @Override
+  public boolean equals(Object obj) {
+    if(obj == null) return false;
+    if(!(obj instanceof Constant constant)) return false;
+    return this.value == constant.value;
+  }
+}

src/main/java/viewer/FunctionList.java

 package viewer;
 
+import formula.Constant;
 import javafx.scene.chart.XYChart;
 
 import java.util.ArrayList;
@@ -18,9 +19,8 @@ class FunctionList {
     this.lowerBound = functionChart.getLowerBound();
     this.upperBound = functionChart.getUpperBound();
 
-    // TODO: add functions
-
-
+    PlottableFunction function = new PlottableFunction(new Constant(1), "f");
+    addFunctionAndItsDerivative(function);
   }
 
   void toggleFunction(PlottableFunction function) {

src/main/java/viewer/MainAppController.java

@@ -45,6 +45,7 @@ public class MainAppController implements Initializable {
     Button button = new Button(function.toString());
     addButton(button);
     button.setOnAction(event -> toggleFunction(function));
+    toggleFunction(function);
   }
 
   private void toggleFunction(PlottableFunction function){

src/test/java/ConstantTest.java

+import formula.Constant;
+import formula.Formula;
+import org.junit.jupiter.api.Test;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.within;
+
+public class ConstantTest {
+  @Test
+  public void testEval(){
+    Constant constantTen = new Constant(10);
+    assertThat(constantTen.eval(0.)).isCloseTo(10., within(.001));
+    Constant constantOne = new Constant(1);
+    assertThat(constantOne.eval(10.)).isCloseTo(1., within(.001));
+  }
+
+  @Test
+  public void testToString(){
+    Constant constantTen = new Constant(10);
+    assertThat(constantTen.toString()).isEqualTo("10.0");
+    Constant constantOne = new Constant(1);
+    assertThat(constantOne.toString()).isEqualTo("1.0");
+  }
+
+  @Test
+  public void testEquals() {
+    Constant constantTen = new Constant(10);
+    Constant constantTen2 = new Constant(10);
+    Constant constantOne = new Constant(0);
+    assertThat(constantTen).isEqualTo(constantTen);
+    assertThat(constantTen).isEqualTo(constantTen2);
+    assertThat(constantTen).isNotEqualTo(constantOne);
+  }
+
+  @Test
+  public void testDerivative() {
+    Constant constantTen = new Constant(10);
+    Formula derivedConstant = constantTen.derivative();
+    assertThat(derivedConstant.eval(10.)).isCloseTo(0., within(.001));
+    Constant constantZero = new Constant(0);
+    assertThat(derivedConstant).isEqualTo(constantZero);
+  }
+}