Merge pull request #113 from LarryHsiao/constant_source

Constant source

src/main/java/com/larryhsiao/clotho/ConstSource.java

@@ -0,0 +1,16 @@
+package com.larryhsiao.clotho;
+
+/**
+ * Constant source
+ */
+public class ConstSource<T> implements Source<T> {
+
+    private final T constant;
+
+    public ConstSource(T constant) {this.constant = constant;}
+
+    @Override
+    public T value() throws Exception {
+        return constant;
+    }
+}

src/test/java/com/larryhsiao/clotho/ConstSourceTest.java

@@ -0,0 +1,18 @@
+package com.larryhsiao.clotho;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Test for {@link ConstSource}.
+ */
+class ConstSourceTest {
+    @Test
+    void inputEqualsOutput() throws Exception {
+        final Object object = new Object();
+        Assertions.assertEquals(
+            object,
+            new ConstSource<>(object).value()
+        );
+    }
+}