diff --git a/Project.toml b/Project.toml
index 1094442..47109c2 100644
--- a/Project.toml
+++ b/Project.toml
@@ -7,3 +7,9 @@ JuliaSyntax = "70703baa-626e-46a2-a12c-08ffd08c73b4"
 
 [compat]
 JuliaSyntax = "0.4.8"
+
+[extras]
+Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
+
+[target]
+test = ["Test"]
diff --git a/test/runtests.jl b/test/runtests.jl
new file mode 100644
index 0000000..6f177f1
--- /dev/null
+++ b/test/runtests.jl
@@ -0,0 +1,62 @@
+using Runic:
+    format_string
+using Test:
+    @test, @testset
+
+@testset "Hex/oct/bin literal integers" begin
+    z(n) = "0"^n
+    test_cases = [
+        # Hex UInt8
+        ("0x" * z(n) * "1" => "0x01" for n in  0:1)...,
+        # Hex  UInt16
+        ("0x" * z(n) * "1" => "0x0001" for n in  2:3)...,
+        # Hex  UInt32
+        ("0x" * z(n) * "1" => "0x00000001" for n in  4:7)...,
+        # Hex  UInt64
+        ("0x" * z(n) * "1" => "0x0000000000000001" for n in  8:15)...,
+        # Hex UInt128
+        ("0x" * z(n) * "1" => "0x" * z(31) * "1" for n in 16:31)...,
+        # Hex BigInt
+        ("0x" * z(n) * "1" => "0x" * z(n) * "1" for n in 32:35)...,
+        # Octal UInt8
+        ("0o" * z(n) * "1" => "0o001" for n in 0:2)...,
+        "0o377" => "0o377", # typemax(UInt8)
+        # Octal UInt16
+        "0o400"    => "0o000400", # typemax(UInt8) + 1
+        ("0o" * z(n) * "1" => "0o000001" for n in 3:5)...,
+        "0o177777" => "0o177777", # typemax(UInt16)
+        # Octal UInt32
+        "0o200000" => "0o00000200000", # typemax(UInt16) + 1
+        ("0o" * z(n) * "1" => "0o00000000001" for n in 6:10)...,
+        "0o37777777777" => "0o37777777777", # typemax(UInt32)
+        # Octal UInt64
+        "0o40000000000" => "0o0000000000040000000000", # typemax(UInt32) + 1
+        ("0o" * z(n) * "1" => "0o" * z(21) * "1" for n in 11:21)...,
+        "0o1777777777777777777777" => "0o1777777777777777777777", # typemax(UInt64)
+        # Octal UInt128
+        "0o2" * z(21) => "0o" * z(21) * "2" * z(21), # typemax(UInt64) + 1
+        ("0o" * z(n) * "1" => "0o" * z(42) * "1" for n in 22:42)...,
+        "0o3" * "7"^42 => "0o3" * "7"^42, # typemax(UInt128)
+        # Octal BigInt
+        "0o4" * z(42) => "0o4" * z(42), # typemax(UInt128) + 1
+        "0o7" * z(42) => "0o7" * z(42),
+    ]
+    # Test the test cases :)
+    mod = Module()
+    for (a, b) in test_cases
+        c = Core.eval(mod, Meta.parse(a))
+        d = Core.eval(mod, Meta.parse(b))
+        @test c == d
+        @test typeof(c) == typeof(d)
+    end
+    # Join all cases to a single string so that we only need to call the formatter once
+    input_str = let io = IOBuffer()
+        join(io, (case.first for case in test_cases), '\n')
+        String(take!(io))
+    end
+    output_str = let io = IOBuffer()
+        join(io, (case.second for case in test_cases), '\n')
+        String(take!(io))
+    end
+    @test format_string(input_str) == output_str
+end