build: test LogError

Closes #34

build/error_test.go

@@ -0,0 +1,72 @@
+package build
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"log"
+	"testing"
+
+	"github.com/mmcloughlin/avo/src"
+)
+
+func TestLogErrorNil(t *testing.T) {
+	var buf bytes.Buffer
+	l := log.New(&buf, "prefix: ", 0)
+	LogError(l, nil, 0)
+	if buf.String() != "" {
+		t.Fatalf("should print nothing for nil error")
+	}
+}
+
+func TestLogErrorNonErrorList(t *testing.T) {
+	var buf bytes.Buffer
+	l := log.New(&buf, "prefix: ", 0)
+	err := errors.New("not an ErrorList")
+	LogError(l, err, 0)
+	got := buf.String()
+	expect := "prefix: " + err.Error() + "\n"
+	if got != expect {
+		t.Fatalf("got\t%q\nexpect\t%q\n", got, expect)
+	}
+}
+
+func TestLogErrorList(t *testing.T) {
+	var buf bytes.Buffer
+	l := log.New(&buf, "prefix: ", 0)
+
+	e := ErrorList{}
+	filename := "asm.go"
+	err := errors.New("some kind of error")
+	n := 7
+	for i := 1; i <= n; i++ {
+		p := src.Position{Filename: filename, Line: i}
+		e.AddAt(p, err)
+	}
+
+	expect := ""
+	// Unlimited print.
+	LogError(l, e, 0)
+	for i := 1; i <= n; i++ {
+		expect += fmt.Sprintf("prefix: %s:%d: some kind of error\n", filename, i)
+	}
+
+	// Max equal to number of errors.
+	LogError(l, e, n)
+	for i := 1; i <= n; i++ {
+		expect += fmt.Sprintf("prefix: %s:%d: some kind of error\n", filename, i)
+	}
+
+	// Max less than number of errors.
+	m := n / 2
+	LogError(l, e, m)
+	for i := 1; i <= m; i++ {
+		expect += fmt.Sprintf("prefix: %s:%d: some kind of error\n", filename, i)
+	}
+	expect += fmt.Sprintf("prefix: too many errors\n")
+
+	got := buf.String()
+	if got != expect {
+		t.Fatalf("got\n%s\nexpect\n%s\n", got, expect)
+	}
+}