BAEL-900 Guide to dynamic tests in Junit 5 (#1860)

junit5/src/test/java/com/baeldung/DynamicTestsExample.java

@@ -0,0 +1,129 @@
+package com.baeldung;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+
+import org.junit.jupiter.api.DynamicTest;
+import org.junit.jupiter.api.TestFactory;
+import org.junit.jupiter.api.function.ThrowingConsumer;
+
+public class DynamicTestsExample {
+
+    @TestFactory
+    Collection<DynamicTest> dynamicTestsWithCollection() {
+        return Arrays.asList(
+          DynamicTest.dynamicTest("Add test", () -> assertEquals(2, Math.addExact(1, 1))),
+          DynamicTest.dynamicTest("Multiply Test", () -> assertEquals(4, Math.multiplyExact(2, 2))));
+    }
+    
+    @TestFactory
+    Iterable<DynamicTest> dynamicTestsWithIterable() {
+        return Arrays.asList(
+          DynamicTest.dynamicTest("Add test", () -> assertEquals(2, Math.addExact(1, 1))),
+          DynamicTest.dynamicTest("Multiply Test", () -> assertEquals(4, Math.multiplyExact(2, 2))));
+    }
+    
+    @TestFactory
+    Iterator<DynamicTest> dynamicTestsWithIterator() {
+        return Arrays.asList(
+          DynamicTest.dynamicTest("Add test", () -> assertEquals(2, Math.addExact(1, 1))),
+          DynamicTest.dynamicTest("Multiply Test", () -> assertEquals(4, Math.multiplyExact(2, 2))))
+          .iterator();
+    }
+    
+    @TestFactory
+    Stream<DynamicTest> dynamicTestsFromIntStream() {
+        return IntStream.iterate(0, n -> n + 2).limit(10).mapToObj(
+          n -> DynamicTest.dynamicTest("test" + n, () -> assertTrue(n % 2 == 0)));
+    }
+    
+    @TestFactory
+    Stream<DynamicTest> dynamicTestsFromStream() {
+
+        // sample input and output
+        List<String> inputList =
+            new ArrayList<>(Arrays.asList("www.somedomain.com", "www.anotherdomain.com", "www.yetanotherdomain.com"));
+        List<String> outputList =
+            new ArrayList<>(Arrays.asList("154.174.10.56", "211.152.104.132", "178.144.120.156"));
+
+        // input generator that generates inputs using inputList
+        Iterator<String> inputGenerator = new Iterator<String>() {
+
+            String current;
+            int size = inputList.size();
+            int index = 0;
+            
+            @Override
+            public boolean hasNext() {
+                if(index == size) {
+                    return false;
+                }
+                current = inputList.get(index);
+                index++;
+                return true;
+            }
+
+            @Override
+            public String next() {
+                return current;
+            }
+        };
+
+        // a display name generator that creates a different name based on the input
+        Function<String, String> displayNameGenerator = (input) -> "Resolving: " + input;
+
+        // the test executor, which actually has the logic of how to execute the test case
+        DomainNameResolver resolver = new DomainNameResolver();
+        ThrowingConsumer<String> testExecutor = (input) -> {
+            int id = inputList.indexOf(input);
+            assertEquals(outputList.get(id), resolver.resolveDomain(input));
+        };
+
+        // combine everything and return a Stream of DynamicTest
+        return DynamicTest.stream(inputGenerator, displayNameGenerator, testExecutor);
+    }
+    
+    @TestFactory
+    Stream<DynamicTest> dynamicTestsFromStreamInJava8() {
+        
+        DomainNameResolver resolver = new DomainNameResolver();
+        
+        List<String> inputList =
+            new ArrayList<>(Arrays.asList("www.somedomain.com", "www.anotherdomain.com", "www.yetanotherdomain.com"));
+        List<String> outputList =
+            new ArrayList<>(Arrays.asList("154.174.10.56", "211.152.104.132", "178.144.120.156"));
+        
+        return inputList.stream().map(dom -> DynamicTest.dynamicTest("Resolving: " + dom, () -> {
+            int id = inputList.indexOf(dom);
+            assertEquals(outputList.get(id), resolver.resolveDomain(dom));
+        }));
+        
+    }
+
+    class DomainNameResolver {
+        
+        private Map<String, String> ipByDomainName = new HashMap<>();
+        
+        DomainNameResolver() {
+            this.ipByDomainName.put("www.somedomain.com", "154.174.10.56");
+            this.ipByDomainName.put("www.anotherdomain.com", "211.152.104.132");
+            this.ipByDomainName.put("www.yetanotherdomain.com", "178.144.120.156");
+        }
+        
+        public String resolveDomain(String domainName) {
+            return ipByDomainName.get(domainName);
+        }
+    }
+
+}