add lab3 tests

src/test/java/IntegralCalculatorTests.java

@@ -1,6 +1,8 @@
 import org.junit.jupiter.api.Test;
 import ru.lionarius.IntegralCalculator;
 
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.function.BiConsumer;
 import java.util.function.Function;
 
 import static org.junit.jupiter.api.Assertions.*;
@@ -50,4 +52,44 @@ class IntegralCalculatorTests {
         assertIntegral(-0.5, calculator, function, upperBound, lowerBound);
         assertIntegral(0.0, calculator, function, lowerBound, lowerBound);
     }
+
+    @Test
+    public void testProgressCallbackDifferentBounds() {
+        final var currentStep = new AtomicLong();
+        final var totalSteps = new AtomicLong();
+        final var callbackCount = new AtomicLong(0);
+
+        final BiConsumer<Long, Long> progressCallback = (current, total) -> {
+            currentStep.set(current);
+            totalSteps.set(total);
+            callbackCount.incrementAndGet();
+        };
+
+        final var calculator = new IntegralCalculator(0.01, progressCallback);
+
+        calculator.calculate(x -> x, 0, 1);
+
+        assertTrue(callbackCount.get() >= 2, "Callback should be called at least twice");
+        assertEquals(totalSteps.get(), currentStep.get(), "Final progress should be equal to total steps");
+    }
+
+    @Test
+    public void testProgressCallbackSameBounds() {
+        var currentStep = new AtomicLong();
+        var totalSteps = new AtomicLong();
+        var callbackCount = new AtomicLong(0);
+
+        BiConsumer<Long, Long> progressCallback = (current, total) -> {
+            currentStep.set(current);
+            totalSteps.set(total);
+            callbackCount.incrementAndGet();
+        };
+
+        var calculator = new IntegralCalculator(0.01, progressCallback);
+
+        calculator.calculate(x -> x, 0, 0);
+
+        assertTrue(callbackCount.get() >= 2, "Callback should be called at least twice");
+        assertEquals(totalSteps.get(), currentStep.get(), "Final progress should be equal to total steps");
+    }
 }