Throw error when envvar is missing and provide unit tests

mvn-defaults/pom.xml

@@ -573,6 +573,9 @@
                     </includes>
                     <useSystemClassLoader>false
                     </useSystemClassLoader> <!-- fixes reflection tests -->
+                    <environmentVariables>
+                        <TEST_ENV_VAR>value</TEST_ENV_VAR>
+                    </environmentVariables>
                 </configuration>
             </plugin>
 

nb-engine/nb-engine-cli/src/main/java/io/nosqlbench/engine/cli/atfiles/NBAtFile.java

@@ -169,8 +169,9 @@ public class NBAtFile {
             String word = iter.next();
             String modified = word.replaceAll("\\$\\{DIR}",parent.toString());
             Optional<String> interpolatedString = NBEnvironment.INSTANCE.interpolate(modified);
+	    String value = interpolatedString.orElseThrow(() -> new RuntimeException("Unable to find environment variable or property in text '"+modified+"' in atfile '" + atPath + "'"));
             iter.remove();
-            iter.add(interpolatedString.orElse(""));
+            iter.add(value);
         }
         return formatted;
     }

nb-engine/nb-engine-cli/src/test/java/io/nosqlbench/engine/cli/atfiles/NBAtFileTest.java

@@ -91,4 +91,15 @@ class NBAtFileTest {
         assertThat(strings).containsExactly("arg1","arg1","arg1","arg2","arg3","arg3","arg3","deepval");
     }
 
+    @Test
+    public void testAtfileEnvironmentVariable() {
+        LinkedList<String> strings = NBAtFile.includeAt("@src/test/resources/atfiles/environment_variable.yaml");
+        assertThat(strings).containsExactly("My value environment");
+    }
+
+    @Test
+    public void testAtfileMissingEnvironmentVariable() {
+        assertThrows(RuntimeException.class, () -> NBAtFile.includeAt("@src/test/resources/atfiles/environment_variable_missing.yaml:>:"));
+    }
+
 }

nb-engine/nb-engine-cli/src/test/resources/atfiles/environment_variable_missing.yaml

@@ -0,0 +1 @@
+- My ${MISSING_ENV_VAR} environment

nb-engine/nb-engine-cli/src/test/resources/atfiles/envronment_variable.yaml

@@ -0,0 +1 @@
+- My ${TEST_ENV_VAR} environment