diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
index 4cd07a7..a83e5b1 100644
--- a/.github/workflows/build.yaml
+++ b/.github/workflows/build.yaml
@@ -26,8 +26,32 @@ jobs:
       - name: Install test runner
         run: go install gotest.tools/gotestsum@latest
 
-      - name: Test
-        run: gotestsum -f github-actions ./...
+      - name: Tests
+        run: |
+            gotestsum -f github-actions ./...
+
+  coverage:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Go
+        uses: actions/setup-go@v4
+        with:
+          go-version: stable
+
+      - name: Coverage
+        run: |
+            go test \
+              -coverprofile cover.out \
+              -covermode    count \
+              -coverpkg     ./... \
+              -shuffle      on \
+              ./...
+
+      - name: Report
+        run: go tool cover -func=cover.out
 
   build-release:
     runs-on: ubuntu-latest
diff --git a/.gitignore b/.gitignore
index 8f0f0f7..a1cd97b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,3 +8,4 @@ a.o
 *.orig
 *.tmp
 *~
+/cover.out
diff --git a/docs/COUNTDOWN.asm b/docs/COUNTDOWN.asm
index aac73c9..832765f 100644
--- a/docs/COUNTDOWN.asm
+++ b/docs/COUNTDOWN.asm
@@ -1,4 +1,4 @@
-;;; countdown.asm : a program for a tutorial that counts down to blast off
+;;; COUNTDOWN.asm : a program for a tutorial that counts down to blast off
 ;;; Inputs: R0 is the address of counter.
 
     .ORIG   x3000               ; Start at the beginning of user-space memory.
diff --git a/docs/TUTORIAL.md b/docs/TUTORIAL.md
index 1e0d2ca..33e0250 100644
--- a/docs/TUTORIAL.md
+++ b/docs/TUTORIAL.md
@@ -333,7 +333,7 @@ create machine code from source. In this directory you will find an assembly
 program. To translate the source to an object file containing machine code, run:
 
 ```console
-$ elsie asm countdown.asm
+$ elsie asm COUNTDOWN.asm
 ```
 
 Well, that isn't satisfying, but no output means success in this case.
@@ -354,7 +354,7 @@ Options:
 ```
 
 ```console
-$ elsie asm -debug countdown.asm
+$ elsie asm -debug COUNTDOWN.asm
  TIMESTAMP : 2023-10-11T11:51:30-04:00
      LEVEL : DEBUG
     SOURCE : asm.go:66
@@ -398,7 +398,7 @@ Before running the countdown program, let's take a look at the source code to
 get an idea what it is going to do.
 
 ```
-;;; countdown.asm : a program for a tutorial that counts down to blast off
+;;; COUNTDOWN.asm : a program for a tutorial that counts down to blast off
 ;;; Inputs: R0 is the address of counter.
 
     .ORIG   x3000               ; Start at the beginning of user-space memory.