add first test

project/plugins.sbt

@@ -1,2 +1,3 @@
 addSbtPlugin("org.scalameta"             % "sbt-scalafmt" % "2.3.4")
 addSbtPlugin("io.github.davidgregory084" % "sbt-tpolecat" % "0.1.13")
+addSbtPlugin("org.scoverage" % "sbt-scoverage" % "1.6.1")

src/main/scala/com/htmlism/mos6502/dsl/DslDemo.scala

@@ -120,7 +120,7 @@ class CPU {
 }
 
 class AssemblyContext {
-  val xs: ListBuffer[Statement] =
+  private val xs: ListBuffer[Statement] =
     ListBuffer()
 
   def push(instruction: Instruction): Unit =
@@ -139,4 +139,9 @@ class AssemblyContext {
     xs.map(_.toAsm)
       .foreach(println)
   }
+
+  def triplets: List[(String, Option[String], Option[String])] =
+    xs
+      .map(_.toTriplet)
+      .toList
 }

src/main/scala/com/htmlism/mos6502/dsl/Statement.scala

@@ -1,9 +1,12 @@
 package com.htmlism.mos6502.dsl
 
+import cats.implicits._
 import com.htmlism.mos6502.model.Instruction
 
 sealed trait Statement {
   def toAsm: String
+
+  def toTriplet: (String, Option[String], Option[String])
 }
 
 case class UnaryInstruction(instruction: Instruction, comment: Option[String]) extends Statement {
@@ -18,6 +21,9 @@ case class UnaryInstruction(instruction: Instruction, comment: Option[String]) e
         left
     }
   }
+
+  def toTriplet: (String, Option[String], Option[String]) =
+    (instruction.toString, None, comment)
 }
 
 case class InstructionWithOperand[A](instruction: Instruction, operand: A, comment: Option[String])(
@@ -37,4 +43,7 @@ case class InstructionWithOperand[A](instruction: Instruction, operand: A, comme
         f"$left%-5s $operandStr"
     }
   }
+
+  def toTriplet: (String, Option[String], Option[String]) =
+    (instruction.toString, ev.toAddressLiteral(operand).some, comment)
 }

src/test/scala/com/htmlism/mos6502/dsl/Easy6502Spec.scala

@@ -0,0 +1,41 @@
+package com.htmlism.mos6502.dsl
+
+import cats.implicits._
+import org.scalatest._
+import flatspec._
+import matchers._
+
+class Easy6502Spec extends AnyFlatSpec with should.Matchers {
+
+  "the three pixel demo" should "have the right instructions" in {
+    val doc =
+      withAssemblyContext { implicit ctx =>
+        val scr =
+          IndexedAddressCollection[Color](0x0200, "screen")
+
+        scr.write(0, Color.White)
+        scr.write(1, Color.Green)
+        scr.write(2, Color.Orange)
+      }
+
+    doc.triplets shouldEqual List(
+      ("LDA", "#$01".some, "write White to screen (0)".some),
+      ("STA", "$0200".some, "".some),
+      ("LDA", "#$05".some, "write Green to screen (1)".some),
+      ("STA", "$0201".some, "".some),
+      ("LDA", "#$08".some, "write Orange to screen (2)".some),
+      ("STA", "$0202".some, "".some)
+    )
+
+    doc.printOut()
+  }
+
+  def withAssemblyContext(f: AssemblyContext => Unit): AssemblyContext = {
+    val ctx: AssemblyContext =
+      new AssemblyContext
+
+    f(ctx)
+
+    ctx
+  }
+}