1 files changed, 129 insertions, 0 deletions
diff --git a/internal/tui/tui_test.go b/internal/tui/tui_test.go
new file mode 100644
index 0000000..6918859
--- /dev/null
+++ b/internal/tui/tui_test.go
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package tui
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestColourNeedsTerminalAndNoNOCOLOR(t *testing.T) {
+	var buf bytes.Buffer
+	if Colour(&buf) {
+		t.Error("colour on a non-terminal writer")
+	}
+
+	old := isTerminal
+	t.Cleanup(func() { isTerminal = old })
+	isTerminal = func(fd int) bool { return true }
+
+	t.Setenv("NO_COLOR", "")
+	os.Unsetenv("NO_COLOR")
+	if !Colour(os.Stdout) {
+		t.Error("no colour on a terminal with NO_COLOR unset")
+	}
+	t.Setenv("NO_COLOR", "1")
+	if Colour(os.Stdout) {
+		t.Error("colour emitted with NO_COLOR set")
+	}
+	t.Setenv("NO_COLOR", "")
+	if Colour(os.Stdout) {
+		t.Error("NO_COLOR set to the empty string must still disable colour")
+	}
+}
+
+func TestHeight(t *testing.T) {
+	var buf bytes.Buffer
+	if h := Height(&buf); h != 0 {
+		t.Errorf("Height on a non-terminal writer = %d, want 0", h)
+	}
+
+	oldT, oldS := isTerminal, termSize
+	t.Cleanup(func() { isTerminal, termSize = oldT, oldS })
+	isTerminal = func(fd int) bool { return true }
+	termSize = func(fd int) (int, int, error) { return 80, 24, nil }
+
+	if h := Height(os.Stdout); h != 24 {
+		t.Errorf("Height = %d, want 24", h)
+	}
+}
+
+func TestPageUsesPagerOnlyWhenTaller(t *testing.T) {
+	dir := t.TempDir()
+	marker := filepath.Join(dir, "paged")
+	// A pager that records what it was given.
+	t.Setenv("PAGER", "tee "+marker)
+
+	oldT, oldS := isTerminal, termSize
+	t.Cleanup(func() { isTerminal, termSize = oldT, oldS })
+	isTerminal = func(fd int) bool { return true }
+	termSize = func(fd int) (int, int, error) { return 80, 5, nil }
+
+	var buf bytes.Buffer
+	if err := Page(&buf, "one\ntwo\n"); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := os.Stat(marker); !os.IsNotExist(err) {
+		t.Error("short text went through the pager")
+	}
+	if buf.String() != "one\ntwo\n" {
+		t.Errorf("short text = %q", buf.String())
+	}
+
+	tall := strings.Repeat("line\n", 20)
+	if err := Page(&buf, tall); err != nil {
+		t.Fatal(err)
+	}
+	b, err := os.ReadFile(marker)
+	if err != nil {
+		t.Fatalf("tall text did not reach the pager: %v", err)
+	}
+	if string(b) != tall {
+		t.Errorf("the pager received %q", b)
+	}
+}
+
+func TestPageCountsFinalLineWithoutTrailingNewline(t *testing.T) {
+	dir := t.TempDir()
+	marker := filepath.Join(dir, "paged")
+	t.Setenv("PAGER", "tee "+marker)
+
+	oldT, oldS := isTerminal, termSize
+	t.Cleanup(func() { isTerminal, termSize = oldT, oldS })
+	isTerminal = func(fd int) bool { return true }
+	termSize = func(fd int) (int, int, error) { return 80, 5, nil }
+
+	// Six lines but only five newlines: one more line than the terminal's
+	// height, with no trailing newline after the last one.
+	text := "one\ntwo\nthree\nfour\nfive\nsix"
+
+	var buf bytes.Buffer
+	if err := Page(&buf, text); err != nil {
+		t.Fatal(err)
+	}
+	b, err := os.ReadFile(marker)
+	if err != nil {
+		t.Fatalf("six lines with no trailing newline, one more than the terminal's height, did not reach the pager: %v", err)
+	}
+	if string(b) != text {
+		t.Errorf("the pager received %q", b)
+	}
+}
+
+func TestReadKeyOnAPipeReadsOneByte(t *testing.T) {
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatal(err)
+	}
+	go func() { w.WriteString("ay"); w.Close() }()
+	got, err := ReadKey(r)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != 'a' {
+		t.Errorf("key = %q, want 'a'", got)
+	}
+}