diff --git a/core/mod_test.ts b/core/mod_test.ts
index e1a61e24..dc977ae2 100644
--- a/core/mod_test.ts
+++ b/core/mod_test.ts
@@ -1,20 +1,129 @@
 import { all, cmd, fs } from "@chiezo/amber";
+import { afterEach, beforeEach, describe, it } from "@std/testing/bdd";
+import { assertSpyCallArg } from "@std/testing/mock";
 import { collect } from "./mod.ts";
+import { assertEquals, assertExists } from "@std/assert";
+import dedent from "dedent";
 
-Deno.test("Molt", { ignore: true }, async () => {
-  cmd.stub("git");
-  all(cmd, fs).mock();
+const MOD_TS = dedent`
+import "jsr:@luca/flag@1.0.0";
+`;
 
-  const deps = await collect({
-    config: "deno.json",
-    lock: "deno.lock",
-  });
+const DENO_JSON = dedent`
+{
+  "imports": {
+    "@luca/flag": "jsr:@luca/flag@^1.0.0",
+  }
+}
+`;
 
-  for (const dep of deps) {
-    const update = await dep.check();
-    if (update) {
-      await update.write();
-      await update.commit();
+const DENO_LOCK = dedent`
+{
+  "version": "3",
+  "packages": {
+    "specifiers": {
+      "jsr:@luca/flag@^1.0.0": "jsr:@luca/flag@1.0.0"
+    },
+    "jsr": {
+      "@luca/flag@1.0.0": {
+        "integrity": "1c76cf54839a86d0929a619c61bd65bb73d7d8a4e31788e48c720dbc46c5d546"
+      }
     }
+  },
+  "remote": {},
+  "workspace": {
+    "dependencies": [
+      "jsr:@luca/flag@^1.0.0"
+    ]
   }
+}
+`;
+
+describe("core", () => {
+  let git: cmd.Stub<"git">;
+
+  beforeEach(async () => {
+    git = cmd.stub("git");
+    all(cmd, fs).mock();
+    await Promise.all([
+      Deno.writeTextFile("mod.ts", MOD_TS),
+      Deno.writeTextFile("deno.json", DENO_JSON),
+      Deno.writeTextFile("deno.lock", DENO_LOCK),
+    ]);
+  });
+
+  afterEach(() => all(cmd, fs).dispose());
+
+  it("should update dependencies in a module", async () => {
+    const deps = await collect({ source: ["mod.ts"] });
+    assertEquals(deps.length, 1);
+    const [dep] = deps;
+    const update = await dep.check();
+    assertExists(update);
+    assertEquals(update.dep.name, "@luca/flag");
+    await update.write();
+    assertEquals(await Deno.readTextFile("deno.json"), DENO_JSON);
+    assertEquals(await Deno.readTextFile("deno.lock"), DENO_LOCK);
+    assertEquals(
+      await Deno.readTextFile("mod.ts"),
+      `import "jsr:@luca/flag@1.0.1";`,
+    );
+    await update.commit();
+    assertSpyCallArg(git, 0, 1, {
+      args: [
+        "commit",
+        "-m",
+        "bump @luca/flag from 1.0.0 to 1.0.1",
+        "mod.ts",
+      ],
+      lock: undefined,
+    });
+  });
+
+  it("should update dependencies in a configuration", async () => {
+    const deps = await collect({ config: "deno.json", lock: "deno.lock" });
+    assertEquals(deps.length, 1);
+    const [dep] = deps;
+    const update = await dep.check();
+    assertExists(update);
+    assertEquals(update.dep.name, "@luca/flag");
+    await update.write();
+    assertEquals(await Deno.readTextFile("mod.ts"), MOD_TS);
+    assertEquals(await Deno.readTextFile("deno.json"), DENO_JSON);
+    assertEquals(
+      await Deno.readTextFile("deno.lock"),
+      dedent`
+        {
+          "version": "3",
+          "packages": {
+            "specifiers": {
+              "jsr:@luca/flag@^1.0.0": "jsr:@luca/flag@1.0.1"
+            },
+            "jsr": {
+              "@luca/flag@1.0.1": {
+                "integrity": "dce7eb4159b1bdb1606fe05c2e5388dcff5ae3b0b84184b934bc623143742408"
+              }
+            }
+          },
+          "remote": {},
+          "workspace": {
+            "dependencies": [
+              "jsr:@luca/flag@^1.0.0"
+            ]
+          }
+        }
+      ` + "\n",
+    );
+    await update.commit();
+    assertSpyCallArg(git, 0, 1, {
+      args: [
+        "commit",
+        "-m",
+        "bump @luca/flag from 1.0.0 to 1.0.1",
+        "deno.json",
+        "deno.lock",
+      ],
+      lock: "deno.lock",
+    });
+  });
 });
diff --git a/core/refs.ts b/core/refs.ts
index c4e53437..53eb0fb9 100644
--- a/core/refs.ts
+++ b/core/refs.ts
@@ -164,7 +164,7 @@ function rewriteImportMap(
   }
   const str = JSON.stringify(json, null, 2);
   const eol = detect(content) ?? EOL;
-  return format(str, eol) + eol;
+  return format(str, eol) + (content.at(-1) === eol ? eol : "");
 }
 
 /** Options for committing the updated dependency. */
diff --git a/deno.json b/deno.json
index 9f180323..4ddb89c9 100644
--- a/deno.json
+++ b/deno.json
@@ -3,7 +3,7 @@
     "cache": "deno task -q ls | xargs deno cache",
     "check": "deno task -q ls | xargs deno check",
     "ls": "ls ./lib/*.ts ./core/*.ts ./integration/*.ts ./cli/*.ts ./cli/src/*.ts",
-    "pre-commit": "deno fmt && deno lint && deno task -q check && deno task -q test:unit",
+    "pre-commit": "deno fmt && deno lint && deno task -q check && deno task -q test",
     "run": "deno run -A --env --unstable-kv ./cli/main.ts",
     "test": "deno test -A --unstable-kv --no-check",
     "update:commit": "deno task -q run --commit --prefix 'chore:' --pre-commit=check,test:unit"