Allow specifying test generators to run through command-line (#307)

generators/Exercise.cs

@@ -1,14 +1,13 @@
 using Generators.Input;
 using Generators.Output;
-using Humanizer;
 
 namespace Generators
 {
     public abstract class Exercise
     {
         protected Exercise()
         {
-            Name = GetType().Name.Kebaberize();
+            Name = GetType().ToExerciseName();
             CanonicalData = CanonicalDataParser.Parse(Name);
             Configuration = new ExerciseConfiguration();
         }

generators/ExerciseCollection.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using Generators.Output;
+
+namespace Generators
+{
+    public class ExerciseCollection : IEnumerable<Exercise>
+    {
+        private readonly string[] _exerciseNames;
+
+        public ExerciseCollection() => _exerciseNames = null;
+        public ExerciseCollection(string[] exerciseNames) => _exerciseNames = exerciseNames;
+
+        public IEnumerator<Exercise> GetEnumerator() => GetDefinedGenerators().GetEnumerator();
+
+        IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+
+        private IEnumerable<Exercise> GetDefinedGenerators() =>
+            from type in Assembly.GetEntryAssembly().GetTypes()
+            where IsConcreteExercise(type) && ShouldBeIncluded(type)
+            select (Exercise)Activator.CreateInstance(type);
+
+        private static bool IsConcreteExercise(Type type) => typeof(Exercise).IsAssignableFrom(type) && !type.GetTypeInfo().IsAbstract;
+
+        private bool ShouldBeIncluded(Type type) 
+            => _exerciseNames == null || 
+               _exerciseNames.Contains(type.ToExerciseName(), StringComparer.OrdinalIgnoreCase) || 
+               _exerciseNames.Contains(type.Name, StringComparer.OrdinalIgnoreCase);
+    }
+}

generators/Output/NameExtensions.cs

@@ -1,10 +1,13 @@
+using System;
 using System.Text.RegularExpressions;
 using Humanizer;
 
 namespace Generators.Output
 {
     public static class NameExtensions
     {
+        public static string ToExerciseName(this Type exerciseType) => exerciseType.Name.Kebaberize();
+
         public static string ToTestClassName(this string input) => $"{input.Dehumanize()}Test";
 
         public static string ToTestedClassName(this string input) => input.Dehumanize();

generators/Program.cs

@@ -5,10 +5,10 @@ namespace Generators
 {
     public static class Program
     {
-        public static void Main()
+        public static void Main(string[] args)
         {
             SetupLogger();
-            GenerateAll();
+            Generate(args);
         }
 
         private static void SetupLogger()
@@ -18,14 +18,17 @@ private static void SetupLogger()
                 .CreateLogger();
         }
 
-        private static void GenerateAll()
+        private static void Generate(string[] exerciseNames)
         {
             Log.Information("Generating tests...");
 
-            foreach (var exercise in new ExerciseCollection())
+            foreach (var exercise in GetExercises(exerciseNames))
                 exercise.Generate();
 
             Log.Information("Generated tests.");
         }
+
+        private static ExerciseCollection GetExercises(string[] exerciseNames) 
+            => exerciseNames.Length == 0 ? new ExerciseCollection() : new ExerciseCollection(exerciseNames);
     }
 }