From 611afab48f28ac5e2e269059a06806caad8296c2 Mon Sep 17 00:00:00 2001
From: Sourabh Bhat <heySourabh@gmail.com>
Date: Thu, 17 Aug 2023 13:26:10 +0200
Subject: [PATCH] return optional ofNullable, as the boundary condition may be
 undefined during initialization.

---
 src/main/mesh/Boundary.java      |  6 +++---
 test/main/mesh/BoundaryTest.java | 31 +++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 3 deletions(-)
 create mode 100644 test/main/mesh/BoundaryTest.java

diff --git a/src/main/mesh/Boundary.java b/src/main/mesh/Boundary.java
index 5fea216..b85b8d8 100644
--- a/src/main/mesh/Boundary.java
+++ b/src/main/mesh/Boundary.java
@@ -12,8 +12,8 @@ public class Boundary {
     private BoundaryCondition bc;
 
     public Boundary(String name, List<Face> faces, BoundaryCondition bc) {
-        this.name = Objects.requireNonNull(name);
-        this.faces = Objects.requireNonNull(faces);
+        this.name = Objects.requireNonNull(name, "Boundary 'name' cannot be null.");
+        this.faces = Objects.requireNonNull(faces, "Boundary 'faces' cannot be null.");
         this.bc = bc;
     }
 
@@ -22,6 +22,6 @@ public void setBC(BoundaryCondition bc) {
     }
 
     public Optional<BoundaryCondition> bc() {
-        return Optional.of(bc);
+        return Optional.ofNullable(bc);
     }
 }
diff --git a/test/main/mesh/BoundaryTest.java b/test/main/mesh/BoundaryTest.java
new file mode 100644
index 0000000..3c3c3a9
--- /dev/null
+++ b/test/main/mesh/BoundaryTest.java
@@ -0,0 +1,31 @@
+package main.mesh;
+
+import org.junit.Test;
+
+import java.util.List;
+import java.util.Optional;
+
+import static org.junit.Assert.*;
+
+public class BoundaryTest {
+
+    @Test
+    public void constructor_nullability_test() {
+        // null name
+        assertThrows(NullPointerException.class, () -> new Boundary(null, List.of(), null));
+        // null faces
+        assertThrows(NullPointerException.class, () -> new Boundary("name", null, null));
+    }
+
+    @Test
+    public void bc_optionality_test() {
+        Boundary bnd = new Boundary("bnd name", List.of(), null);
+        assertEquals(Optional.empty(), bnd.bc());
+    }
+
+    @Test
+    public void trying_to_set_null_bc() {
+        Boundary bnd = new Boundary("bnd name", List.of(), null);
+        assertThrows(NullPointerException.class, () -> bnd.setBC(null));
+    }
+}
\ No newline at end of file