Wrote tests with TestFX

javafx-template/src/main/java/app/AppController.java

@@ -19,6 +19,15 @@ public class AppController {
         calc = new Calc(0.0, 0.0, 0.0);
     }
 
+    public Calc getCalc() {
+        return calc;
+    }
+
+    public void setCalc(Calc calc) {
+        this.calc = calc;
+        updateOperandsView();
+    }
+
     @FXML
     private ListView<Double> operandsView;
 

javafx-template/src/test/java/app/AppTest.java

@@ -3,22 +3,130 @@ package app;
 import javafx.fxml.FXMLLoader;
 import javafx.scene.Parent;
 import javafx.scene.Scene;
+import javafx.scene.control.Label;
+import javafx.scene.control.ListView;
 import javafx.stage.Stage;
 
 import java.io.IOException;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+import org.opentest4j.AssertionFailedError;
 import org.testfx.framework.junit5.ApplicationTest;
+import org.testfx.matcher.control.LabeledMatchers;
 
 /**
  * TestFX App test
  */
 public class AppTest extends ApplicationTest {
 
+    private AppController controller;
+    private Parent root;
+
     @Override
     public void start(Stage stage) throws IOException {
         FXMLLoader fxmlLoader = new FXMLLoader(this.getClass().getResource("App.fxml"));
-        Parent parent = fxmlLoader.load();
-        stage.setScene(new Scene(parent));
+        root = fxmlLoader.load();
+        controller = fxmlLoader.getController();
+        stage.setScene(new Scene(root));
         stage.show();
     }
+
+    public Parent getRootNode() {
+        return root;
+    }
+
+    private String enterLabel = """
+        E
+        n
+        t
+        e
+        r
+        """.stripTrailing();
+
+    private void click(String... labels) {
+        for (var label : labels) {
+            clickOn(LabeledMatchers.hasText(label));
+        }
+    }
+
+    private String getOperandString() {
+        return ((Label) getRootNode().lookup("#operandView")).getText();
+    }
+
+    private ListView<Double> getOperandsView() {
+        return (ListView<Double>) getRootNode().lookup("#operandsView");
+    }
+
+    private void checkView(double... operands) {
+        for (int i = 0; i < operands.length; i++) {
+            Assertions.assertEquals(operands[i], controller.getCalc().peekOperand(i), "Wrong value at #" + i + " of operand stack");
+        }
+        List<Double> viewItems = getOperandsView().getItems();
+        for (int i = 0; i < operands.length; i++) {
+            Assertions.assertEquals(operands[i], viewItems.get(viewItems.size() - i - 1), "Wrong value at #" + i + " of operands view");
+        }
+    }
+
+    private void checkView(String operandString, double... operands) {
+        Assertions.assertEquals(operandString, getOperandString());
+        checkView(operands);
+    }
+
+    // see https://www.baeldung.com/parameterized-tests-junit-5
+    // about @ParameterizedTest
+
+    @ParameterizedTest
+    @MethodSource
+    public void testClicksOperand(String labels, String operandString) {
+        for (var label : labels.split(" ")) {
+            click(label);
+        }
+        checkView(operandString);
+    }
+
+    private static Stream<Arguments> testClicksOperand() {
+        return Stream.of(
+            Arguments.of("2 7", "27"),
+            Arguments.of("2 7 .", "27."),
+            Arguments.of("2 7 . 5", "27.5"),
+            Arguments.of("2 7 . 5 .", "27.")
+        );
+    }
+    
+    @ParameterizedTest
+    @MethodSource
+    public void testClicksOperands(String labels, String operandsString) {
+        for (var label : labels.split(" ")) {
+            click(label.equals("\n") ? enterLabel : label);
+        }
+        checkView(Stream.of(operandsString.split(" ")).mapToDouble(Double::valueOf).toArray());
+    }
+
+    private static Stream<Arguments> testClicksOperands() {
+        return Stream.of(
+            Arguments.of("2 7 . 5 \n", "27.5"),
+            Arguments.of("2 7 \n", "27.0"),
+            Arguments.of("2 \n 7 \n 5 \n", "5.0", "7.0", "2.0"),
+            Arguments.of("2 7 . \n", "27.0"),
+            Arguments.of("2 7 . 5 \n", "27.5"),
+            Arguments.of("2 \n 7 +", "9.0"),
+            Arguments.of("2 \n 7 -", "-5.0"),
+            Arguments.of("2 \n 7 *", "14.0"),
+            Arguments.of("6 \n 3 /", "2.0"),
+            Arguments.of("2 5 \n √", "5.0")
+        );
+    }
+
+    @Test
+    public void testPi() {
+        click("π");
+        checkView("", Math.PI);
+    }
 }