diff --git a/.gitignore b/.gitignore
index 44c5847d..115b359d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,3 +6,6 @@ target/
 
 # local environment
 .env
+
+# coverage
+.coverage/
diff --git a/sqlx-mysql/src/protocol/handshake.rs b/sqlx-mysql/src/protocol/handshake.rs
index 12f09960..68bbe0c7 100644
--- a/sqlx-mysql/src/protocol/handshake.rs
+++ b/sqlx-mysql/src/protocol/handshake.rs
@@ -99,7 +99,7 @@ impl Deserialize<'_> for Handshake {
                 // read to NUL or read to the end if we can't find a NUL
 
                 let auth_plugin_name_end =
-                    memchr(b'\0', &buf).map(|end| end - 1).unwrap_or(buf.len());
+                    memchr(b'\0', &buf).unwrap_or(buf.len());
 
                 // UNSAFE: auth plugin names are known to be ASCII
                 #[allow(unsafe_code)]
diff --git a/tests/x.py b/tests/x.py
new file mode 100755
index 00000000..73bc5016
--- /dev/null
+++ b/tests/x.py
@@ -0,0 +1,107 @@
+#!/usr/bin/env python3
+import sys
+from os import environ
+from shutil import rmtree
+from pathlib import Path
+from json import loads
+import argparse
+import subprocess
+from subprocess import Popen, check_call, check_output, PIPE
+
+parser = argparse.ArgumentParser()
+parser.add_argument("-v", "--verbose", action="store_true")
+parser.add_argument("-t", "--target")
+parser.add_argument("-l", "--list-targets", action="store_true")
+
+argv, unknown = parser.parse_known_args()
+
+# get an absolute path to the project directory for SQLx
+project_dir = Path(__file__).parent.parent
+coverage_dir = project_dir.joinpath(".coverage")
+raw_coverage_dir = project_dir.joinpath("raw")
+
+# global test filenames
+# we capture these all so we can collect coverage later
+test_object_filenames = []
+
+def run(cmd, env, cwd, comment=None):
+    if comment is not None:
+        print(f"\x1b[2m # {comment}\x1b[0m")
+
+    print(f"\x1b[93m $ {' '.join(cmd)}\x1b[0m")
+
+    subprocess.run(cmd, env=env, cwd=project_dir, check=True,
+                   stdout=None if argv.verbose else PIPE)
+
+def run_unit_test(project_name: str):
+    project = f"sqlx-{project_name}"
+    tag = f"unit:{project_name}"
+
+    if argv.target is not None and argv.target not in tag:
+        return
+
+    if argv.list_targets:
+        print(tag)
+        return
+
+    env = environ.copy()
+    env["RUSTFLAGS"] = "-Zinstrument-coverage -Aunused"
+    env["LLVM_PROFILE_FILE"] = f"{project_dir}/.coverage/raw/{project}_%m.profraw"
+
+    # run the tests
+    run([
+        "cargo", "+nightly", "test",
+        "--manifest-path", f"{project}/Cargo.toml",
+    ], env=env, cwd=project_dir, comment=f"unit test {project}")
+
+    # build the test binaries and outputs a big pile of JSON that can help
+    # us figure out the test binary filename (needed for coverage results)
+    messages = subprocess.run([
+        "cargo", "+nightly", "test",
+        "--manifest-path", f"{project}/Cargo.toml",
+        "--no-run", "--message-format=json"
+    ], env=env, cwd=project_dir, check=True, capture_output=True).stdout
+
+    # use jq to extract the test filenames from the json blob
+    # TODO: use python json to remove the dependency on jq
+    filenames = check_output([
+        "jq", "-r", "select(.profile.test == true) | .filenames[]",
+    ], env=env, cwd=project_dir, input=messages).decode().strip().split("\n")
+
+    test_object_filenames.extend(filter(lambda fn: not fn.endswith(".dSYM"), filenames))
+
+def main():
+    # remove and re-create directory for raw coverage data
+    raw_coverage_dir = Path(f"{project_dir}/.coverage/raw/")
+    rmtree(raw_coverage_dir)
+    raw_coverage_dir.mkdir()
+
+    # run unit tests, collect test binary filenames
+    run_unit_test("core")
+    run_unit_test("mysql")
+
+    if test_object_filenames:
+        # merge raw profile data into a single profile
+        check_call([
+            "cargo", "profdata", "--", "merge",
+            "--sparse",
+            "-o", f"{project_dir}/.coverage/sqlx.profdata",
+            *raw_coverage_dir.glob("*.profraw"),
+        ], cwd=project_dir)
+
+        # export indexed profile data
+        coverage_file = coverage_dir.joinpath("sqlx.lcov")
+        coverage_file.write_bytes(check_output([
+            "cargo", "cov", "--", "export",
+            "--format=lcov",
+            "-Xdemangler=rustfilt",
+            "--ignore-filename-regex", "/.cargo/registry",
+            "--instr-profile", f"{project_dir}/.coverage/sqlx.profdata",
+            *map(lambda fn: f"--object={fn}", test_object_filenames),
+        ], cwd=project_dir))
+
+        # generate HTML coverage report
+        check_output(["genhtml", "-o", coverage_dir, coverage_file], cwd=project_dir)
+
+if __name__ == '__main__':
+    main()