first init

crc_test.go

@@ -0,0 +1,106 @@
+package modbus
+
+import (
+	"testing"
+)
+
+func TestCRC(t *testing.T) {
+	var c	crc
+	var out	[]byte
+
+	// initialize the CRC object and make sure we get 0xffff as init value
+	c.init()
+	if c.crc != 0xffff {
+		t.Errorf("expected 0xffff, saw 0x%04x", c.crc)
+	}
+
+	out = c.value()
+	if len(out) != 2 {
+		t.Errorf("value() should have returned 2 bytes, got %v", len(out))
+	}
+	if out[0] != 0xff || out[1] != 0xff {
+		t.Errorf("expected {0xff, 0xff} got {0x%02x, 0x%02x}", out[0], out[1])
+	}
+
+	// add a few bytes, check the output
+	c.add([]byte{0x01, 0x02, 0x03, 0x04, 0x05})
+	if c.crc != 0xbb2a {
+		t.Errorf("expected 0xbb2a, saw 0x%04x", c.crc)
+	}
+
+	out = c.value()
+	if len(out) != 2 {
+		t.Errorf("value() should have returned 2 bytes, got %v", len(out))
+	}
+	if out[0] != 0x2a || out[1] != 0xbb {
+		t.Errorf("expected {0x2a, 0xbb} got {0x%02x, 0x%02x}", out[0], out[1])
+	}
+
+	// add one extra byte, test the output again
+	c.add([]byte{0x06})
+	if c.crc != 0xddba {
+		t.Errorf("expected 0xddba, saw 0x%04x", c.crc)
+	}
+
+	out = c.value()
+	if len(out) != 2 {
+		t.Errorf("value() should have returned 2 bytes, got %v", len(out))
+	}
+	if out[0] != 0xba || out[1] != 0xdd {
+		t.Errorf("expected {0xba, 0xdd} got {0x%02x, 0x%02x}", out[0], out[1])
+	}
+
+	// init the CRC once again: the output bytes should be back to 0xffff
+	c.init()
+	if c.crc != 0xffff {
+		t.Errorf("expected 0xffff, saw 0x%04x", c.crc)
+	}
+
+	out = c.value()
+	if len(out) != 2 {
+		t.Errorf("value() should have returned 2 bytes, got %v", len(out))
+	}
+	if out[0] != 0xff || out[1] != 0xff {
+		t.Errorf("expected {0xff, 0xff} got {0x%02x, 0x%02x}", out[0], out[1])
+	}
+
+	return
+}
+
+func TestCRCIsEqual(t *testing.T) {
+	var c	crc
+	var out	[]byte
+
+	// initialize the CRC object and feed it a few bytes
+	c.init()
+	c.add([]byte{0x01, 0x02, 0x03, 0x04, 0x05, 0x06})
+
+	// make sure the register value is what it should be
+	if c.crc != 0xddba {
+		t.Errorf("expected 0xddba, saw 0x%04x", c.crc)
+	}
+
+	// positive test
+	if !c.isEqual(0xba, 0xdd) {
+		t.Error("isEqual() should have returned true")
+	}
+
+	// negative test
+	if c.isEqual(0xdd, 0xba) {
+		t.Error("isEqual() should have returned false")
+	}
+
+	// loopback test
+	out = c.value()
+	if !c.isEqual(out[0], out[1]) {
+		t.Error("isEqual() should have returned true")
+	}
+
+	// an empty payload should have a CRC of 0xffff
+	c.init()
+	if !c.isEqual(0xff, 0xff) {
+		t.Error("isEqual() should have returned true")
+	}
+
+	return
+}