diff --git a/lib/intcode/assembler.ex b/lib/intcode/assembler.ex
index 0c1ba2d..c51036a 100644
--- a/lib/intcode/assembler.ex
+++ b/lib/intcode/assembler.ex
@@ -67,16 +67,39 @@ defmodule Assembler do
         it -> it
       end)
 
-    IO.inspect(labels)
+    # IO.inspect(labels)
     Enum.reverse(memory)
   end
 
-  def repeat(_, 0), do: []
-  def repeat(n, count), do: [n | repeat(n, count - 1)]
+  @doc """
+  Raises the base to to the given power.
 
+  ## Examples
+    iex> Assembler.pow(10, 3)
+    1000
+    iex> Assembler.pow(5, 4)
+    625
+  """
   def pow(base, 1), do: base
   def pow(base, exp), do: base * pow(base, exp - 1)
 
+  @doc """
+  Parses assembly instruction parameter values and modes.
+
+  ## Examples
+    iex> Assembler.parse_params("1 2 3", [:read, :read, :read])
+    {[1, 2, 3], 11100}
+    iex> Assembler.parse_params("1 2 3", [:read, :read, :write])
+    {[1, 2, 3], 1100}
+    iex> Assembler.parse_params("1 2 $3", [:read, :read, :write])
+    {[1, 2, 3], 1100}
+    iex> Assembler.parse_params("$1 2 3", [:read, :read, :write])
+    {[1, 2, 3], 1000}
+    iex> Assembler.parse_params("$label 2 3", [:read, :read, :write])
+    {[{:label, "label"}, 2, 3], 1000}
+    iex> Assembler.parse_params("1 label 3", [:read, :read, :write])
+    {[1, {:label, "label"}, 3], 1100}
+  """
   def parse_params(params, param_types) do
     params
     |> String.split(" ")
@@ -110,54 +133,130 @@ defmodule Assembler do
     end)
   end
 
+  @doc """
+  Assembles the given instruction and adds it to the memory (in reverse order).
+  """
   def assemble_instruction(insn, memory \\ [])
 
+  @doc """
+  Assemble add instruction.
+
+  ## Examples
+    iex> Assembler.assemble_instruction("add 1 2 3")
+    [3, 2, 1, 1101]
+  """
   def assemble_instruction("add " <> params, memory) do
     {[a, b, dest], modes} = parse_params(params, [:read, :read, :write])
 
     [dest, b, a, 1 + modes | memory]
   end
 
+  @doc """
+  Assemble multiply instruction.
+
+  ## Examples
+    iex> Assembler.assemble_instruction("mul 1 2 3")
+    [3, 2, 1, 1102]
+  """
   def assemble_instruction("mul " <> params, memory) do
     {[a, b, dest], modes} = parse_params(params, [:read, :read, :write])
 
     [dest, b, a, 2 + modes | memory]
   end
 
+  @doc """
+  Assemble halt instruction.
+
+  ## Examples
+    iex> Assembler.assemble_instruction("hlt")
+    [99]
+  """
   def assemble_instruction("hlt", memory) do
     [99 | memory]
   end
 
+  @doc """
+  Assemble input instruction.
+
+  ## Examples
+    iex> Assembler.assemble_instruction("in 7")
+    [7, 3]
+  """
   def assemble_instruction("in " <> params, memory) do
     {[dest], modes} = parse_params(params, [:write])
 
     [dest, 3 + modes | memory]
   end
 
+  @doc """
+  Assemble input instruction.
+
+  ## Examples
+    iex> Assembler.assemble_instruction("out 7")
+    [7, 104]
+    iex> Assembler.assemble_instruction("out $7")
+    [7, 4]
+  """
   def assemble_instruction("out " <> params, memory) do
     {[val], modes} = parse_params(params, [:read])
 
     [val, 4 + modes | memory]
   end
 
+  @doc """
+  Assemble jump-if-non-zero instruction.
+
+  ## Examples
+    iex> Assembler.assemble_instruction("jnz 1 2")
+    [2, 1, 105]
+    iex> Assembler.assemble_instruction("jnz $var 2")
+    [2, {:label, "var"}, 5]
+  """
   def assemble_instruction("jnz " <> params, memory) do
     {[target, dest], modes} = parse_params(params, [:read, :read])
 
     [dest, target, 5 + modes | memory]
   end
 
+  @doc """
+  Assemble jump-if-zero instruction.
+
+  ## Examples
+    iex> Assembler.assemble_instruction("jez 1 2")
+    [2, 1, 106]
+    iex> Assembler.assemble_instruction("jez $var 2")
+    [2, {:label, "var"}, 6]
+  """
   def assemble_instruction("jez " <> params, memory) do
     {[target, dest], modes} = parse_params(params, [:read, :read])
 
     [dest, target, 6 + modes | memory]
   end
 
+  @doc """
+  Assemble compare-less-than instruction.
+
+  ## Examples
+    iex> Assembler.assemble_instruction("clt 1 2 3")
+    [3, 2, 1, 1107]
+    iex> Assembler.assemble_instruction("clt $1 $2 3")
+    [3, 2, 1, 7]
+  """
   def assemble_instruction("clt " <> params, memory) do
     {[a, b, dest], modes} = parse_params(params, [:read, :read, :write])
 
     [dest, b, a, 7 + modes | memory]
   end
 
+  @doc """
+  Assemble compare-equal instruction.
+
+  ## Examples
+    iex> Assembler.assemble_instruction("ceq 1 2 3")
+    [3, 2, 1, 1108]
+    iex> Assembler.assemble_instruction("ceq $1 $2 3")
+    [3, 2, 1, 8]
+  """
   def assemble_instruction("ceq " <> params, memory) do
     {[a, b, dest], modes} = parse_params(params, [:read, :read, :write])
 
diff --git a/test/intcode/assembler_test.exs b/test/intcode/assembler_test.exs
new file mode 100644
index 0000000..df526d9
--- /dev/null
+++ b/test/intcode/assembler_test.exs
@@ -0,0 +1,71 @@
+defmodule AssemblerTest do
+  use ExUnit.Case
+  doctest Assembler
+
+  test "assembles empty program" do
+    assert Assembler.assemble("") == []
+  end
+
+  test "assembles simple program" do
+    program = """
+      add 1 2 10
+      mul 2 3 11
+      add $10 $11 12
+      hlt
+    """
+
+    assert Assembler.assemble(program) == [
+             1101,
+             1,
+             2,
+             10,
+             1102,
+             2,
+             3,
+             11,
+             1,
+             10,
+             11,
+             12,
+             99
+           ]
+  end
+
+  test "assembles simple program with a label" do
+    program = """
+      add 1 2 10
+      jnz $10 nonZero
+    nonZero:
+      hlt
+    """
+
+    assert Assembler.assemble(program) == [
+             1101,
+             1,
+             2,
+             10,
+             1005,
+             10,
+             7,
+             99
+           ]
+  end
+
+  test "assembles a simple program with a data label" do
+    program = """
+      add 1 2 var
+      out $var
+    var: 0
+    """
+
+    assert Assembler.assemble(program) == [
+             1101,
+             1,
+             2,
+             6,
+             4,
+             6,
+             0
+           ]
+  end
+end