basic unit tests for formatToModernDisplay and formatToClassicDisplay

Author: piotr-iohk

app/src/test/java/to/bitkit/models/CurrencyTest.kt

@@ -0,0 +1,40 @@
+package to.bitkit.models
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import java.util.Locale
+
+class CurrencyTest {
+
+    @Test
+    fun `formatToModernDisplay uses space grouping`() {
+        val sats = 123_456_789L
+
+        val formatted = sats.formatToModernDisplay(Locale.US)
+
+        assertEquals("123 456 789", formatted)
+    }
+
+    @Test
+    fun `formatToModernDisplay handles zero`() {
+        val formatted = 0L.formatToModernDisplay(Locale.US)
+
+        assertEquals("0", formatted)
+    }
+
+    @Test
+    fun `formatToClassicDisplay always shows eight decimals`() {
+        val formatted = 0L.formatToClassicDisplay(Locale.US)
+
+        assertEquals("0.00000000", formatted)
+    }
+
+    @Test
+    fun `formatToClassicDisplay converts sats to btc`() {
+        val sats = 12_345L // 0.00012345 BTC
+
+        val formatted = sats.formatToClassicDisplay(Locale.US)
+
+        assertEquals("0.00012345", formatted)
+    }
+}