Add more and unify tests for absent object cases

- Unify test data for nonexistence of an object/string and collection.
- Introduce more test through adding missing test data to existing tests.
- Improve logic for checking absence of values to match tests.
- Add missing tests for absent value validation.
- Update documentation to include shared test functionality.

src/application/Common/Array.ts

@@ -1,7 +1,7 @@
 // Compares to Array<T> objects for equality, ignoring order
 export function scrambledEqual<T>(array1: readonly T[], array2: readonly T[]) {
-  if (!array1) { throw new Error('undefined first array'); }
-  if (!array2) { throw new Error('undefined second array'); }
+  if (!array1) { throw new Error('missing first array'); }
+  if (!array2) { throw new Error('missing second array'); }
   const sortedArray1 = sort(array1);
   const sortedArray2 = sort(array2);
   return sequenceEqual(sortedArray1, sortedArray2);
@@ -12,8 +12,8 @@ export function scrambledEqual<T>(array1: readonly T[], array2: readonly T[]) {
 
 // Compares to Array<T> objects for equality in same order
 export function sequenceEqual<T>(array1: readonly T[], array2: readonly T[]) {
-  if (!array1) { throw new Error('undefined first array'); }
-  if (!array2) { throw new Error('undefined second array'); }
+  if (!array1) { throw new Error('missing first array'); }
+  if (!array2) { throw new Error('missing second array'); }
   if (array1.length !== array2.length) {
     return false;
   }

src/application/Common/Enum.ts

@@ -21,7 +21,7 @@ function parseEnumValue<T extends EnumType, TEnumValue extends EnumType>(
   enumVariable: EnumVariable<T, TEnumValue>,
 ): TEnumValue {
   if (!value) {
-    throw new Error(`undefined ${enumName}`);
+    throw new Error(`missing ${enumName}`);
   }
   if (typeof value !== 'string') {
     throw new Error(`unexpected type of ${enumName}: "${typeof value}"`);
@@ -54,8 +54,8 @@ export function assertInRange<T extends EnumType, TEnumValue extends EnumType>(
   value: TEnumValue,
   enumVariable: EnumVariable<T, TEnumValue>,
 ) {
-  if (value === undefined) {
-    throw new Error('undefined enum value');
+  if (value === undefined || value === null) {
+    throw new Error('absent enum value');
   }
   if (!(value in enumVariable)) {
     throw new RangeError(`enum value "${value}" is out of range`);

src/application/Common/ScriptingLanguage/ScriptingLanguageFactory.ts

@@ -20,7 +20,7 @@ export abstract class ScriptingLanguageFactory<T> implements IScriptingLanguageF
   protected registerGetter(language: ScriptingLanguage, getter: Getter<T>) {
     assertInRange(language, ScriptingLanguage);
     if (!getter) {
-      throw new Error('undefined getter');
+      throw new Error('missing getter');
     }
     if (this.getters.has(language)) {
       throw new Error(`${ScriptingLanguage[language]} is already registered`);