SOP commands: Throw UnsupportedSubcommand error when sop.command() returns null

sop-java-picocli/src/test/java/sop/cli/picocli/SOPTest.java

@@ -4,11 +4,26 @@
 
 package sop.cli.picocli;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.mockito.Mockito.mock;
 
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
 import com.ginsberg.junit.exit.ExpectSystemExitWithStatus;
 import org.junit.jupiter.api.Test;
 import sop.SOP;
+import sop.operation.Armor;
+import sop.operation.Dearmor;
+import sop.operation.Decrypt;
+import sop.operation.DetachInbandSignatureAndMessage;
+import sop.operation.Encrypt;
+import sop.operation.ExtractCert;
+import sop.operation.GenerateKey;
+import sop.operation.Sign;
+import sop.operation.Verify;
+import sop.operation.Version;
 
 public class SOPTest {
 
@@ -28,4 +43,77 @@ public class SOPTest {
         // At this point, no SOP backend is set, so an InvalidStateException triggers exit(1)
         SopCLI.main(new String[] {"armor"});
     }
+
+    @Test
+    public void UnsupportedSubcommandsTest() {
+        SOP nullCommandSOP = new SOP() {
+            @Override
+            public Version version() {
+                return null;
+            }
+
+            @Override
+            public GenerateKey generateKey() {
+                return null;
+            }
+
+            @Override
+            public ExtractCert extractCert() {
+                return null;
+            }
+
+            @Override
+            public Sign sign() {
+                return null;
+            }
+
+            @Override
+            public Verify verify() {
+                return null;
+            }
+
+            @Override
+            public Encrypt encrypt() {
+                return null;
+            }
+
+            @Override
+            public Decrypt decrypt() {
+                return null;
+            }
+
+            @Override
+            public Armor armor() {
+                return null;
+            }
+
+            @Override
+            public Dearmor dearmor() {
+                return null;
+            }
+
+            @Override
+            public DetachInbandSignatureAndMessage detachInbandSignatureAndMessage() {
+                return null;
+            }
+        };
+        SopCLI.setSopInstance(nullCommandSOP);
+
+        List<String[]> commands = new ArrayList<>();
+        commands.add(new String[] {"armor"});
+        commands.add(new String[] {"dearmor"});
+        commands.add(new String[] {"decrypt"});
+        commands.add(new String[] {"detach-inband-signature-and-message"});
+        commands.add(new String[] {"encrypt"});
+        commands.add(new String[] {"extract-cert"});
+        commands.add(new String[] {"generate-key"});
+        commands.add(new String[] {"sign"});
+        commands.add(new String[] {"verify", "signature.asc", "cert.asc"});
+        commands.add(new String[] {"version"});
+
+        for (String[] command : commands) {
+            int exit = SopCLI.execute(command);
+            assertEquals(69, exit, "Unexpected exit code for non-implemented command " + Arrays.toString(command) + ": " + exit);
+        }
+    }
 }