diff --git a/packages/cultcache-ts/test/decode-document-payload.test.ts b/packages/cultcache-ts/test/decode-document-payload.test.ts
index 92fd2146..a63859ee 100644
--- a/packages/cultcache-ts/test/decode-document-payload.test.ts
+++ b/packages/cultcache-ts/test/decode-document-payload.test.ts
@@ -31,3 +31,9 @@ test("a payload is read by its definition's formatter, a codec's, or as a plain
   // Without the definition the codec payload is its positional array, which is why a caller that holds one passes it.
   assert.deepEqual(decodeDocumentPayload(undefined, encode(["a", 1])), ["a", 1]);
 });
+
+test("a definition that declares both a codec and a formatter is refused where its payload is read", () => {
+  const both = { ...codec, formatter: formatted.formatter } as typeof codec;
+  assert.throws(() => decodeDocumentPayload(both, encode(["a", 1])), (error: Error) =>
+    error.message === 'CultCache document type "t.codec" declares both a codec and a formatter.');
+});
diff --git a/packages/cultmesh-browser/test/cultmesh-browser.test.ts b/packages/cultmesh-browser/test/cultmesh-browser.test.ts
index 61b560c2..fb65fbf3 100644
--- a/packages/cultmesh-browser/test/cultmesh-browser.test.ts
+++ b/packages/cultmesh-browser/test/cultmesh-browser.test.ts
@@ -982,3 +982,8 @@ test("decodeCultNetPayload reads a payload through the formatter it is given, an
   assert.deepEqual(decodeCultNetPayload<{ count: number }>(record, formatter), { count: 7 });
   assert.deepEqual(decodeCultNetPayload<number[]>(record), [7]);
 });
+
+test("decodeCultNetPayload refuses a payload that is not messagepack, naming the encoding and not the payload", () => {
+  const record = { schemaId: "t.v0", recordKey: "k", payloadEncoding: "json", payload: encodeWireValue("secret-value") } as unknown as CultNetRawDocumentRecord;
+  assert.throws(() => decodeCultNetPayload(record), (error: Error) => error.message === "Unsupported CultNet document payload 'json'.");
+});
diff --git a/packages/cultmesh-browser/test/payload-decode-owner.test.ts b/packages/cultmesh-browser/test/payload-decode-owner.test.ts
index 5ed8f915..e5a23f78 100644
--- a/packages/cultmesh-browser/test/payload-decode-owner.test.ts
+++ b/packages/cultmesh-browser/test/payload-decode-owner.test.ts
@@ -1,6 +1,6 @@
 import assert from "node:assert/strict";
-import { readdirSync, readFileSync } from "node:fs";
-import { join } from "node:path";
+import { existsSync, readdirSync, readFileSync } from "node:fs";
+import { dirname, join } from "node:path";
 import { fileURLToPath } from "node:url";
 import test from "node:test";
 
@@ -10,7 +10,11 @@ import test from "node:test";
 // Limits: a text scan. It reads the package's src files for the module specifier and the manifest for the dependency
 // name. It does not follow a re-export from another package, a specifier assembled at run time, or a hand-written
 // decoder; the dependency absence is what makes the specifier unresolvable here when the workspace does not hoist it.
-const root = fileURLToPath(new URL("../../", import.meta.url));
+// The package root: the nearest directory above this file (compiled or run in place) that holds a package.json.
+function packageRoot(from: string): string {
+  return existsSync(join(from, "package.json")) ? from : packageRoot(dirname(from));
+}
+const root = packageRoot(dirname(fileURLToPath(import.meta.url)));
 
 function sourceFiles(dir: string): string[] {
   return readdirSync(dir, { withFileTypes: true }).flatMap((entry) =>
@@ -23,7 +27,7 @@ test("no source file imports msgpack and the manifest does not list it", () => {
     assert.equal(manifest[section]?.["@msgpack/msgpack"], undefined, section);
   }
   const files = sourceFiles(join(root, "src"));
-  assert.ok(files.length > 5, "fixture: the scan reads the package's sources");
+  assert.ok(files.length >= 1, "fixture: the scan reads the package's sources");
   const offenders = files.filter((file) => /@msgpack\/msgpack/.test(readFileSync(file, "utf8")));
   assert.deepEqual(offenders, []);
 });
diff --git a/packages/cultmesh-ts/test/payload-decode-owner.test.ts b/packages/cultmesh-ts/test/payload-decode-owner.test.ts
index e267a9c2..f6471bb4 100644
--- a/packages/cultmesh-ts/test/payload-decode-owner.test.ts
+++ b/packages/cultmesh-ts/test/payload-decode-owner.test.ts
@@ -1,6 +1,6 @@
 import assert from "node:assert/strict";
-import { readdirSync, readFileSync } from "node:fs";
-import { join } from "node:path";
+import { existsSync, readdirSync, readFileSync } from "node:fs";
+import { dirname, join } from "node:path";
 import test from "node:test";
 
 // A document payload is decoded by cultcache-ts alone (decodeDocumentPayload); every other value on a wire goes through
@@ -9,7 +9,11 @@ import test from "node:test";
 // Limits: a text scan. It reads the package's src files for the module specifier and the manifest for the dependency
 // name. It does not follow a re-export from another package, a specifier assembled at run time, or a hand-written
 // decoder; the dependency absence is what makes the specifier unresolvable here when the workspace does not hoist it.
-const root = join(__dirname, "..", "..");
+// The package root: the nearest directory above this file (compiled or run in place) that holds a package.json.
+function packageRoot(from: string): string {
+  return existsSync(join(from, "package.json")) ? from : packageRoot(dirname(from));
+}
+const root = packageRoot(__dirname);
 
 function sourceFiles(dir: string): string[] {
   return readdirSync(dir, { withFileTypes: true }).flatMap((entry) =>
@@ -22,7 +26,7 @@ test("no source file imports msgpack and the manifest does not list it", () => {
     assert.equal(manifest[section]?.["@msgpack/msgpack"], undefined, section);
   }
   const files = sourceFiles(join(root, "src"));
-  assert.ok(files.length > 5, "fixture: the scan reads the package's sources");
+  assert.ok(files.length >= 1, "fixture: the scan reads the package's sources");
   const offenders = files.filter((file) => /@msgpack\/msgpack/.test(readFileSync(file, "utf8")));
   assert.deepEqual(offenders, []);
 });