1 files changed, 94 insertions, 0 deletions
diff --git a/internal/plan/placeholder_test.go b/internal/plan/placeholder_test.go
new file mode 100644
index 0000000..e155430
--- /dev/null
+++ b/internal/plan/placeholder_test.go
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package plan
+
+import (
+	"strings"
+	"testing"
+	"time"
+)
+
+func facts() Facts {
+	return Facts{
+		Name:     "Invoice_2026-08.pdf",
+		Captures: []string{"2026-08", "2026", "a}}b"},
+		ModTime:  time.Date(2026, 8, 15, 14, 30, 45, 0, time.UTC),
+		Now:      time.Date(2026, 9, 12, 9, 0, 0, 0, time.UTC),
+	}
+}
+
+func TestExpand(t *testing.T) {
+	tests := []struct{ in, want string }{
+		{"Work/Acme", "Work/Acme"},
+		{"{name}", "Invoice_2026-08.pdf"},
+		{"{stem}", "Invoice_2026-08"},
+		{"{ext}", ".pdf"},
+		{"{stem}{ext}", "Invoice_2026-08.pdf"},
+		{"Work/{mtime:%Y}", "Work/2026"},
+		{"{mtime:%Y-%m-%d}", "2026-08-15"},
+		{"{mtime:%H%M%S}", "143045"},
+		{"{mtime:%j}", "227"},
+		{"{now:%Y-%m-%d}", "2026-09-12"},
+		{"{1}", "2026"},
+		// D2: an expanded value that itself contains "}}" must reach the
+		// output unchanged. Expand's single-pass scanner jumps past a
+		// placeholder's closing brace, so written bytes are never re-scanned;
+		// a refactor to scan-then-replace would silently re-collapse them.
+		{"{2}", "a}}b"},
+		{"{{literal}}", "{literal}"},
+		{"100{{%}}", "100{%}"},
+		{"{mtime:%Y%%}", "2026%"},
+		{"Photos/{mtime:%Y}/{stem}-{1}{ext}", "Photos/2026/Invoice_2026-08-2026.pdf"},
+	}
+	for _, tt := range tests {
+		got, err := Expand(tt.in, facts())
+		if err != nil || got != tt.want {
+			t.Errorf("Expand(%q) = %q, %v; want %q", tt.in, got, err, tt.want)
+		}
+	}
+}
+
+func TestExpandNoExtension(t *testing.T) {
+	f := facts()
+	f.Name = "README"
+	for in, want := range map[string]string{"{stem}": "README", "{ext}": ""} {
+		if got, err := Expand(in, f); err != nil || got != want {
+			t.Errorf("Expand(%q) on README = %q, %v; want %q", in, got, err, want)
+		}
+	}
+	f.Name = ".bashrc"
+	if got, _ := Expand("{stem}", f); got != ".bashrc" {
+		t.Errorf("dotfile stem = %q, want .bashrc", got)
+	}
+	if got, _ := Expand("{ext}", f); got != "" {
+		t.Errorf("dotfile ext = %q, want empty", got)
+	}
+	f.Name = "archive.tar.gz"
+	if got, _ := Expand("{stem}|{ext}", f); got != "archive.tar|.gz" {
+		t.Errorf("double extension = %q, want archive.tar|.gz", got)
+	}
+}
+
+func TestExpandErrors(t *testing.T) {
+	tests := []struct{ in, want string }{
+		{"{7}", "no capture group 7"},
+		{"{0}", "capture groups are numbered from 1"},
+		{"{whatever}", "unknown placeholder {whatever}"},
+		{"{name", "unclosed placeholder"},
+		{"{mtime:%Q}", "unknown time format %Q in {mtime:...}"},
+		{"{mtime}", "unknown placeholder {mtime}"},
+		// B3: the error must name the placeholder actually written ("now"),
+		// not hardcode "mtime" - the {mtime:%Q} case above passes either
+		// way, which is why that defect survived.
+		{"{now:%Q}", "unknown time format %Q in {now:...}"},
+		// D3: {1}...{9} is the syntax (spec §7.3); {10} and up must be
+		// rejected the same way an unknown placeholder is.
+		{"{10}", "unknown placeholder {10}"},
+	}
+	for _, tt := range tests {
+		_, err := Expand(tt.in, facts())
+		if err == nil || !strings.Contains(err.Error(), tt.want) {
+			t.Errorf("Expand(%q) error = %v; want %q", tt.in, err, tt.want)
+		}
+	}
+}