diff --git a/ch11/adder/Cargo.toml b/ch11/adder/Cargo.toml
index e61cb12..2f47f56 100644
--- a/ch11/adder/Cargo.toml
+++ b/ch11/adder/Cargo.toml
@@ -3,4 +3,8 @@ name = "adder"
 version = "0.1.0"
 edition = "2021"
 
+# [lib]
+# name="lib"
+# path="src/lib.rs"
+
 [dependencies]
diff --git a/ch11/adder/tests/common/mod.rs b/ch11/adder/tests/common/mod.rs
new file mode 100644
index 0000000..f00413c
--- /dev/null
+++ b/ch11/adder/tests/common/mod.rs
@@ -0,0 +1,11 @@
+// Having common appear in the test results with `running 0 tests`
+// is suboptimal. To avoid this, make a file `tests/common/mod.rs`
+
+// Files in the subdirectories of the tests directory don't get compiled
+// as separate crates or have sections in the test output.
+//
+// Can use this file from any of the integration test files as a module.
+
+pub fn setup() {
+    // setup code for specific library's tests would go here
+}
diff --git a/ch11/adder/tests/integration_test.rs b/ch11/adder/tests/integration_test.rs
new file mode 100644
index 0000000..7c25315
--- /dev/null
+++ b/ch11/adder/tests/integration_test.rs
@@ -0,0 +1,15 @@
+// can run with just `cargo test` or
+//   $ cargo test --test integration_test
+// for this file specifically
+
+use adder::add_two;
+
+mod common;
+
+#[test]
+fn it_adds_two() {
+    common::setup();
+
+    let result = add_two(2);
+    assert_eq!(result, 4);
+}