Added zip tests

src/test/kotlin/com/github/michaelbull/result/ZipTest.kt

@@ -0,0 +1,202 @@
+package com.github.michaelbull.result
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class ZipTest {
+
+    data class ZipData3(val a: String, val b: Int, val c: Boolean)
+    data class ZipData4(val a: String, val b: Int, val c: Boolean, val d: Double)
+    data class ZipData5(val a: String, val b: Int, val c: Boolean, val d: Double, val e: Char)
+
+    class Zip {
+
+        @Test
+        fun returnsTransformedValueIfBothOk() {
+            val result = zip(
+                { Ok(10) },
+                { Ok(20) },
+                Int::plus
+            )
+
+            result as Ok
+
+            assertEquals(
+                expected = 30,
+                actual = result.value
+            )
+        }
+
+        @Test
+        fun returnsErrIfOneOfTwoErr() {
+            val result = zip(
+                { Ok(10) },
+                { Ok(20).and { Err("hello") } },
+                Int::plus
+            )
+
+            result as Err
+
+            assertEquals(
+                expected = "hello",
+                actual = result.error
+            )
+        }
+
+        @Test
+        fun returnsFirstErrIfBothErr() {
+            val result = zip(
+                { Ok(10).and { Err("foo") } },
+                { Ok(20).and { Err("bar") } },
+                Int::plus
+            )
+
+            result as Err
+
+            assertEquals(
+                expected = "foo",
+                actual = result.error
+            )
+        }
+
+        @Test
+        fun returnsTransformedValueIfThreeOk() {
+            val result = zip(
+                { Ok("hello") },
+                { Ok(2) },
+                { Ok(false) },
+                ::ZipData3
+            )
+
+            result as Ok
+
+            assertEquals(
+                expected = ZipData3("hello", 2, false),
+                actual = result.value
+            )
+        }
+
+        @Test
+        fun returnsErrIfOneOfThreeErr() {
+            val result = zip(
+                { Ok("foo") },
+                { Ok(1).and { Err("bar") } },
+                { Ok(false) },
+                ::ZipData3
+            )
+
+            result as Err
+
+            assertEquals(
+                expected = "bar",
+                actual = result.error
+            )
+        }
+
+        @Test
+        fun returnsFirstErrIfTwoOfThreeErr() {
+            val result = zip(
+                { Ok("foo") },
+                { Ok(1).and { Err("bar") } },
+                { Ok(false).and { Err("baz") } },
+                ::ZipData3
+            )
+
+            assertEquals(
+                expected = "bar",
+                actual = result.getError()
+            )
+        }
+
+        @Test
+        fun returnsFirstErrIfAllThreeErr() {
+            val result = zip(
+                { Ok("foo").and { Err(1) } },
+                { Ok(1).and { Err(2) } },
+                { Ok(false).and { Err(3) } },
+                ::ZipData3
+            )
+
+            result as Err
+
+            assertEquals(
+                expected = 1,
+                actual = result.error
+            )
+        }
+
+        @Test
+        fun returnsTransformedValueIfFourOk() {
+            val result = zip(
+                { Ok("hello") },
+                { Ok(2) },
+                { Ok(false) },
+                { Ok(1.5) },
+                ::ZipData4
+            )
+
+            result as Ok
+
+            assertEquals(
+                expected = ZipData4("hello", 2, false, 1.5),
+                actual = result.value
+            )
+        }
+
+        @Test
+        fun returnsFirstErrIfSomeOfFourErr() {
+            val result = zip(
+                { Ok("hello") },
+                { Ok(2).and { Err(1) } },
+                { Ok(false) },
+                { Ok(1.5).and { Err(2) } },
+                ::ZipData4
+            )
+
+            result as Err
+
+            assertEquals(
+                expected = 1,
+                actual = result.error
+            )
+        }
+
+        @Test
+        fun returnsTransformedValueIfFiveOk() {
+            val result = zip(
+                { Ok("hello") },
+                { Ok(2) },
+                { Ok(false) },
+                { Ok(1.5) },
+                { Ok('a') },
+                ::ZipData5
+            )
+
+            result as Ok
+
+            assertEquals(
+                expected = ZipData5("hello", 2, false, 1.5, 'a'),
+                actual = result.value
+            )
+        }
+
+        @Test
+        fun returnsFirstErrIfSomeOfFiveErr() {
+            val result = zip(
+                { Ok("hello").and { Err(1) } },
+                { Ok(2) },
+                { Ok(false) },
+                { Ok(1.5) },
+                { Ok('a').and { Err(2) } },
+                ::ZipData5
+            )
+
+            result as Err
+
+            assertEquals(
+                expected = 1,
+                actual = result.error
+            )
+        }
+    }
+}