test: add lnurl amount conversion unit tests

Author: piotr-iohk

app/src/test/java/to/bitkit/ext/LnurlExtTest.kt

@@ -0,0 +1,75 @@
+package to.bitkit.ext
+
+import com.synonym.bitkitcore.LnurlPayData
+import com.synonym.bitkitcore.LnurlWithdrawData
+import org.junit.Test
+import to.bitkit.test.BaseUnitTest
+import kotlin.test.assertEquals
+
+class LnurlExtTest : BaseUnitTest() {
+
+    @Test
+    fun `minSendableSat rounds up when msats not divisible by 1000`() {
+        val data = LnurlPayData(
+            uri = "lnurl",
+            callback = "callback",
+            minSendable = 100_500u,
+            maxSendable = 200_000u,
+            metadataStr = "[]",
+            commentAllowed = null,
+            allowsNostr = false,
+            nostrPubkey = null,
+        )
+
+        assertEquals(101u, data.minSendableSat())
+    }
+
+    @Test
+    fun `minSendableSat keeps exact sat amounts`() {
+        val data = LnurlPayData(
+            uri = "lnurl",
+            callback = "callback",
+            minSendable = 100_000u,
+            maxSendable = 200_000u,
+            metadataStr = "[]",
+            commentAllowed = null,
+            allowsNostr = false,
+            nostrPubkey = null,
+        )
+
+        assertEquals(100u, data.minSendableSat())
+    }
+
+    @Test
+    fun `maxSendableSat floors when msats not divisible by 1000`() {
+        val data = LnurlPayData(
+            uri = "lnurl",
+            callback = "callback",
+            minSendable = 1_000u,
+            maxSendable = 100_999u,
+            metadataStr = "[]",
+            commentAllowed = null,
+            allowsNostr = false,
+            nostrPubkey = null,
+        )
+
+        assertEquals(100u, data.maxSendableSat())
+    }
+
+    @Test
+    fun `minWithdrawableSat rounds up and treats null as zero`() {
+        val nullMin = LnurlWithdrawData(
+            uri = "lnurl",
+            callback = "callback",
+            k1 = "k1",
+            defaultDescription = "desc",
+            minWithdrawable = null,
+            maxWithdrawable = 1_000u,
+            tag = "withdraw",
+        )
+        assertEquals(0u, nullMin.minWithdrawableSat())
+
+        val nonRoundMin = nullMin.copy(minWithdrawable = 1_500u)
+        assertEquals(2u, nonRoundMin.minWithdrawableSat())
+    }
+}