test: improve coverage for builtin/tuple_to_json.mbt

**Disclaimer**: This PR was generated by an LLM agent as part of an experiment.

**Summary:** coverage of builtin/tuple_to_json.mbt: 13.333% -> 100%

Author: rami3l

builtin/tuple_to_json_test.mbt

@@ -13,13 +13,205 @@
 // limitations under the License.
 
 ///|
-test "to_json for tuple of 2 elements" {
+test "2-tuple to_json" {
   let pair = (42, "hello")
   @json.inspect!(pair, content=[42, "hello"])
 }
 
+///|
+test "3-tuple to_json" {
+  let triple = (42, "hello", true)
+  @json.inspect!(triple, content=[42, "hello", true])
+}
+
 ///|
 test "4-tuple to_json" {
-  let tuple : (Int, String, Bool, Double) = (42, "hello", true, 3.14)
+  let tuple = (42, "hello", true, 3.14)
   @json.inspect!(tuple, content=[42, "hello", true, 3.14])
 }
+
+///|
+test "5-tuple to_json" {
+  let tuple = (42, "hello", true, 3.14, 'a')
+  @json.inspect!(tuple, content=[42, "hello", true, 3.14, "a"])
+}
+
+///|
+test "6-tuple to_json" {
+  let tuple = (42, "hello", true, 3.14, 'a', 1)
+  @json.inspect!(tuple, content=[42, "hello", true, 3.14, "a", 1])
+}
+
+///|
+test "7-tuple to_json" {
+  let tuple = (42, "hello", true, 3.14, 'a', 1, "world")
+  @json.inspect!(tuple, content=[42, "hello", true, 3.14, "a", 1, "world"])
+}
+
+///|
+test "8-tuple to_json" {
+  let tuple = (42, "hello", true, 3.14, 'a', 1, "world", false)
+  @json.inspect!(tuple, content=[
+    42, "hello", true, 3.14, "a", 1, "world", false,
+  ])
+}
+
+///|
+test "9-tuple to_json" {
+  let tuple = (42, "hello", true, 3.14, 'a', 1, "world", false, 2.71)
+  @json.inspect!(tuple, content=[
+    42, "hello", true, 3.14, "a", 1, "world", false, 2.71,
+  ])
+}
+
+///|
+test "10-tuple to_json" {
+  let tuple = (42, "hello", true, 3.14, 'a', 1, "world", false, 2.71, 'b')
+  @json.inspect!(tuple, content=[
+    42, "hello", true, 3.14, "a", 1, "world", false, 2.71, "b",
+  ])
+}
+
+///|
+test "11-tuple to_json" {
+  let tuple = (42, "hello", true, 3.14, 'a', 1, "world", false, 2.71, 'b', 43UL)
+  @json.inspect!(tuple, content=[
+    42, "hello", true, 3.14, "a", 1, "world", false, 2.71, "b", "43",
+  ])
+}
+
+///|
+test "12-tuple to_json" {
+  let tuple = (
+    42, "hello", true, 3.14, 'a', 1, "world", false, 2.71, 'b', 43UL, 0x12345678U,
+  )
+  @json.inspect!(tuple, content=[
+    42, "hello", true, 3.14, "a", 1, "world", false, 2.71, "b", "43", 305419896,
+  ])
+}
+
+///|
+test "13-tuple to_json" {
+  let tuple = (
+    42, "hello", true, 3.14, 'a', 1, "world", false, 2.71, 'b', 43UL, 0x12345678U,
+    0x87654321L,
+  )
+  @json.inspect!(tuple, content=[
+    42, "hello", true, 3.14, "a", 1, "world", false, 2.71, "b", "43", 305419896,
+    "2271560481",
+  ])
+}
+
+///|
+test "14-tuple to_json" {
+  let tuple = (
+    42,
+    "hello",
+    true,
+    3.14,
+    'a',
+    1,
+    "world",
+    false,
+    2.71,
+    'b',
+    43UL,
+    0x12345678U,
+    0x87654321L,
+    (0xabcdef, 1234567890UL),
+  )
+  @json.inspect!(tuple, content=[
+    42,
+    "hello",
+    true,
+    3.14,
+    "a",
+    1,
+    "world",
+    false,
+    2.71,
+    "b",
+    "43",
+    305419896,
+    "2271560481",
+    [11259375, "1234567890"],
+  ])
+}
+
+///|
+test "15-tuple to_json" {
+  let tuple = (
+    42,
+    "hello",
+    true,
+    3.14,
+    'a',
+    1,
+    "world",
+    false,
+    2.71,
+    'b',
+    43UL,
+    0x12345678U,
+    0x87654321L,
+    (0xabcdef, 1234567890UL),
+    (0x12345678UL, 0x87654321UL, 0xabcdefUL),
+  )
+  @json.inspect!(tuple, content=[
+    42,
+    "hello",
+    true,
+    3.14,
+    "a",
+    1,
+    "world",
+    false,
+    2.71,
+    "b",
+    "43",
+    305419896,
+    "2271560481",
+    [11259375, "1234567890"],
+    ["305419896", "2271560481", "11259375"],
+  ])
+}
+
+///|
+test "16-tuple to_json" {
+  let tuple = (
+    "hello",
+    42,
+    true,
+    3.14,
+    'a',
+    1,
+    "world",
+    false,
+    2.71,
+    'b',
+    43UL,
+    0x12345678U,
+    0x87654321L,
+    '码',
+    -0.00001,
+    ("wow", [0x87654321UL, 1234567890UL]),
+  )
+  @json.inspect!(tuple, content=[
+    "hello",
+    42,
+    true,
+    3.14,
+    "a",
+    1,
+    "world",
+    false,
+    2.71,
+    "b",
+    "43",
+    305419896,
+    "2271560481",
+    "码",
+    -0.00001,
+    ["wow", ["2271560481", "1234567890"]],
+  ])
+}