Answer architecture round 2: New's doc comment wraps whole, the README's stream needs no seeded, and the system-seed test reports each run's exit code and stderr

README.md

@@ -431,7 +431,7 @@ error on every later call; a `datatype` in a tag other than the one its Go type
 refused, naming that type.
 
 A `*Generator` is safe for concurrent use; a sequence is reproducible only
-when drawn from one goroutine. Changing how a value is composed shifts the seeded
+when drawn from one goroutine. Changing how a value is composed shifts the
 stream for that value and everything drawn after it.
 
 ### Your own CLI

cli/cli_test.go

@@ -6,7 +6,6 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"io"
 	"io/fs"
 	"os"
 	"path/filepath"
@@ -129,10 +128,14 @@ func TestRunDotPath(t *testing.T) {
 }
 
 func TestRunWithoutASeedTakesTheSystemSeed(t *testing.T) {
-	var drawn, seeded bytes.Buffer
-	run("fejkdata", shipped, nil, 42, strings.NewReader("{uuid()}"), &drawn, io.Discard)
-	run("fejkdata", shipped, []string{"--seed", "42"}, 7, strings.NewReader("{uuid()}"), &seeded, io.Discard)
-	if drawn.String() == "" || drawn.String() != seeded.String() {
+	var drawn, seeded, errb bytes.Buffer
+	if code := run("fejkdata", shipped, nil, 42, strings.NewReader("{uuid()}"), &drawn, &errb); code != 0 {
+		t.Fatalf("run with system seed 42 = %d, stderr=%q", code, errb.String())
+	}
+	if code := run("fejkdata", shipped, []string{"--seed", "42"}, 7, strings.NewReader("{uuid()}"), &seeded, &errb); code != 0 {
+		t.Fatalf("run --seed 42 = %d, stderr=%q", code, errb.String())
+	}
+	if drawn.String() != seeded.String() {
 		t.Fatalf("run with system seed 42 = %q, run --seed 42 = %q; want the same draw", drawn.String(), seeded.String())
 	}
 }

fejkdata.go

@@ -96,8 +96,8 @@ func (loadError) Is(target error) bool { return target == ErrLoad }
 // It errors on a missing directory, invalid JSON or invalid data. Given only
 // WithDataFS() with no modules, New loads no data, and the generator renders templates
 // that read none. A source whose .fejkdata.json carries an index, as each shipped
-// module's does, loads each category on the first call reaching it. Data failing to load, in New or on that first call, gives an error matching
-// [ErrLoad].
+// module's does, loads each category on the first call reaching it. Data failing to
+// load, in New or on that first call, gives an error matching [ErrLoad].
 func New(opts ...Option) (*Generator, error) {
 	var c config
 	for _, opt := range opts {