diff --git a/gradle-6/fibonacci-recursive/build.gradle.kts b/gradle-6/fibonacci-recursive/build.gradle.kts
new file mode 100644
index 000000000000..0872a524721f
--- /dev/null
+++ b/gradle-6/fibonacci-recursive/build.gradle.kts
@@ -0,0 +1,17 @@
+plugins {
+    `java-library`
+}
+
+dependencies {
+    api(project(":fibonacci-spi"))
+    compileOnly("com.google.auto.service:auto-service-annotations:1.0-rc6")
+    annotationProcessor("com.google.auto.service:auto-service:1.0-rc6")
+
+    testImplementation(testFixtures(project(":fibonacci-spi")))
+    testImplementation("org.junit.jupiter:junit-jupiter-api:5.5.2")
+    testRuntimeOnly("org.junit.jupiter:junit-jupiter-engine:5.5.2")
+}
+
+tasks.test {
+    useJUnitPlatform()
+}
\ No newline at end of file
diff --git a/gradle-6/fibonacci-recursive/src/main/java/com/baeldung/fibonacci/impl/RecursiveFibonacci.java b/gradle-6/fibonacci-recursive/src/main/java/com/baeldung/fibonacci/impl/RecursiveFibonacci.java
new file mode 100644
index 000000000000..97eccde0548b
--- /dev/null
+++ b/gradle-6/fibonacci-recursive/src/main/java/com/baeldung/fibonacci/impl/RecursiveFibonacci.java
@@ -0,0 +1,20 @@
+package com.baeldung.fibonacci.impl;
+
+import com.baeldung.fibonacci.FibonacciSequenceGenerator;
+import com.google.auto.service.AutoService;
+
+/** Recursive implementation of the {@link FibonacciSequenceGenerator}. */
+@AutoService(FibonacciSequenceGenerator.class)
+public final class RecursiveFibonacci implements FibonacciSequenceGenerator {
+
+  @Override
+  public int generate(int nth) {
+    if (nth < 0) {
+      throw new IllegalArgumentException("sequence number must be 0 or greater");
+    }
+    if (nth <= 1) {
+      return nth;
+    }
+    return generate(nth - 1) + generate(nth - 2);
+  }
+}
diff --git a/gradle-6/fibonacci-recursive/src/test/java/com/baeldung/fibonacci/impl/RecursiveFibonacciUnitTest.java b/gradle-6/fibonacci-recursive/src/test/java/com/baeldung/fibonacci/impl/RecursiveFibonacciUnitTest.java
new file mode 100644
index 000000000000..1e46e7510611
--- /dev/null
+++ b/gradle-6/fibonacci-recursive/src/test/java/com/baeldung/fibonacci/impl/RecursiveFibonacciUnitTest.java
@@ -0,0 +1,16 @@
+package com.baeldung.fibonacci.impl;
+
+import com.baeldung.fibonacci.FibonacciSequenceGenerator;
+import com.baeldung.fibonacci.FibonacciSequenceGeneratorFixture;
+
+/**
+ * Unit test which reuses the {@link FibonacciSequenceGeneratorFixture} test mix-in exported from
+ * the fibonacci-spi project.
+ */
+final class RecursiveFibonacciUnitTest implements FibonacciSequenceGeneratorFixture {
+
+  @Override
+  public FibonacciSequenceGenerator provide() {
+    return new RecursiveFibonacci();
+  }
+}
diff --git a/gradle-6/fibonacci-spi/build.gradle.kts b/gradle-6/fibonacci-spi/build.gradle.kts
new file mode 100644
index 000000000000..e571f329a956
--- /dev/null
+++ b/gradle-6/fibonacci-spi/build.gradle.kts
@@ -0,0 +1,13 @@
+plugins {
+    `java-library`
+    `java-test-fixtures`
+}
+
+dependencies {
+    testFixturesApi("org.junit.jupiter:junit-jupiter-api:5.5.2")
+    testFixturesImplementation("org.junit.jupiter:junit-jupiter-engine:5.5.2")
+}
+
+tasks.test {
+    useJUnitPlatform()
+}
\ No newline at end of file
diff --git a/gradle-6/fibonacci-spi/src/main/java/com/baeldung/fibonacci/FibonacciSequenceGenerator.java b/gradle-6/fibonacci-spi/src/main/java/com/baeldung/fibonacci/FibonacciSequenceGenerator.java
new file mode 100644
index 000000000000..1e9de212576a
--- /dev/null
+++ b/gradle-6/fibonacci-spi/src/main/java/com/baeldung/fibonacci/FibonacciSequenceGenerator.java
@@ -0,0 +1,11 @@
+package com.baeldung.fibonacci;
+
+/** Describes an SPI for a Fibonacci sequence generator function. */
+public interface FibonacciSequenceGenerator {
+
+  /**
+   * @param nth the index of the number in the fibonacci sequence
+   * @return the nth number in the fibonacci sequence
+   */
+  int generate(int nth);
+}
diff --git a/gradle-6/fibonacci-spi/src/testFixtures/java/com/baeldung/fibonacci/FibonacciSequenceGeneratorFixture.java b/gradle-6/fibonacci-spi/src/testFixtures/java/com/baeldung/fibonacci/FibonacciSequenceGeneratorFixture.java
new file mode 100644
index 000000000000..0b7988f64047
--- /dev/null
+++ b/gradle-6/fibonacci-spi/src/testFixtures/java/com/baeldung/fibonacci/FibonacciSequenceGeneratorFixture.java
@@ -0,0 +1,31 @@
+package com.baeldung.fibonacci;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Reusable test fixture for {@link FibonacciSequenceGenerator} implementations. Tests will be
+ * skipped if no such implementation exists.
+ */
+public interface FibonacciSequenceGeneratorFixture {
+
+  /** @return the implementation of {@link FibonacciSequenceGenerator} to test. Must not be null */
+  FibonacciSequenceGenerator provide();
+
+  @Test
+  default void when_sequence_index_is_negative_then_throws() {
+    final FibonacciSequenceGenerator generator = provide();
+    assertThrows(IllegalArgumentException.class, () -> generator.generate(-1));
+  }
+
+  @Test
+  default void when_given_index_then_generates_fibonacci_number() {
+    final FibonacciSequenceGenerator generator = provide();
+    final int[] sequence = {0, 1, 1, 2, 3, 5, 8};
+    for (int i = 0; i < sequence.length; i++) {
+      assertEquals(sequence[i], generator.generate(i));
+    }
+  }
+}
diff --git a/gradle-6/gradle.properties b/gradle-6/gradle.properties
new file mode 100644
index 000000000000..f97ebb7d3349
--- /dev/null
+++ b/gradle-6/gradle.properties
@@ -0,0 +1 @@
+org.gradle.parallel=true
diff --git a/gradle-6/settings.gradle.kts b/gradle-6/settings.gradle.kts
index d84d0ff54e1b..babe43117558 100644
--- a/gradle-6/settings.gradle.kts
+++ b/gradle-6/settings.gradle.kts
@@ -1,6 +1,8 @@
 rootProject.name = "gradle-6"
 
 include("dependency-constraints")
+include("fibonacci-spi")
+include("fibonacci-recursive")
 include("httpclient-platform")
 include("module-metadata-publishing")
 include("person-rest-client")