diff --git a/tests/ecmascript/test-bi-cbor-dec-fastint.js b/tests/ecmascript/test-bi-cbor-dec-fastint.js
new file mode 100644
index 00000000..549f4d9d
--- /dev/null
+++ b/tests/ecmascript/test-bi-cbor-dec-fastint.js
@@ -0,0 +1,154 @@
+/*
+ *  Current CBOR decode fastint behavior.
+ */
+
+/*===
+- top level integer
+17 fastint
+255 fastint
+4275878552 fastint
+4294967295 fastint
+4294967295 fastint
+4294967296 fastint
+139486488458836 fastint
+140737488355327 fastint
+140737488355328
+141685511714388
+-18 fastint
+-256 fastint
+-2147483648 fastint
+-2147483649 fastint
+-4275878553 fastint
+-139486488458837 fastint
+-140737488355328 fastint
+-2147483648 fastint
+-2147483649 fastint
+-140737488355329
+-141685511714389
+- array wrapped integer
+17 fastint
+255 fastint
+4275878552 fastint
+4294967295 fastint
+4294967295
+4294967296
+139486488458836
+140737488355327
+140737488355328
+141685511714388
+-18 fastint
+-256 fastint
+-2147483648 fastint
+-2147483649
+-4275878553
+-2147483648
+-2147483649
+-140737488355329
+-141685511714389
+- integer-compatible double
+17 fastint
+17
+- integer-compatible float
+123 fastint
+123
+- integer-compatible half-float
+123 fastint
+123
+===*/
+
+function test() {
+    var inp, dec;
+
+    function t(arr) {
+        var dec = CBOR.decode(new Uint8Array(arr));
+        var t = Array.isArray(dec) ? dec[0] : dec;
+        var info_t = Duktape.info(t);
+        var info_double = Duktape.info(123.4);
+        if (info_t.itag === info_double.itag) {
+            print(t);
+        } else {
+            print(t, 'fastint');
+        }
+        //print(Duktape.enc('jx', Duktape.info(t)));
+    }
+
+    // If top level value is an integer, it gets coerced into a fastint
+    // because of return value fastint check for CBOR.decode() itself.
+    // This applies to the entire fastint range.
+    print('- top level integer');
+    t([ 0x11 ]);
+    t([ 0x18, 0xff ]);
+    t([ 0x1a, 0xfe, 0xdc, 0xba, 0x98 ]);
+    t([ 0x1a, 0xff, 0xff, 0xff, 0xff ]);
+    t([ 0x1b, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff ]);
+    t([ 0x1b, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00 ]);
+    t([ 0x1b, 0x00, 0x00, 0x7e, 0xdc, 0xba, 0x98, 0x76, 0x54 ]);
+    t([ 0x1b, 0x00, 0x00, 0x7f, 0xff, 0xff, 0xff, 0xff, 0xff ]);
+    t([ 0x1b, 0x00, 0x00, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00 ]);  // no longer in fastint range
+    t([ 0x1b, 0x00, 0x00, 0x80, 0xdc, 0xba, 0x98, 0x76, 0x54 ]);  // no longer in fastint range
+    t([ 0x31 ]);
+    t([ 0x38, 0xff ]);
+    t([ 0x3a, 0x7f, 0xff, 0xff, 0xff ]);
+    t([ 0x3a, 0x80, 0x00, 0x00, 0x00 ]);
+    t([ 0x3a, 0xfe, 0xdc, 0xba, 0x98 ]);
+    t([ 0x3b, 0x00, 0x00, 0x7e, 0xdc, 0xba, 0x98, 0x76, 0x54 ]);
+    t([ 0x3b, 0x00, 0x00, 0x7f, 0xff, 0xff, 0xff, 0xff, 0xff ]);
+    t([ 0x3b, 0x00, 0x00, 0x00, 0x00, 0x7f, 0xff, 0xff, 0xff ]);
+    t([ 0x3b, 0x00, 0x00, 0x00, 0x00, 0x80, 0x00, 0x00, 0x00 ]);
+    t([ 0x3b, 0x00, 0x00, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00 ]);  // no longer in fastint range
+    t([ 0x3b, 0x00, 0x00, 0x80, 0xdc, 0xba, 0x98, 0x76, 0x54 ]);  // no longer in fastint range
+
+    // An integer deeper inside a structure won't get automatic return
+    // value fastint check, so it is up to the CBOR binding to ensure
+    // fastints are used (e.g. use duk_push_int() rather than
+    // duk_push_number() where applicable).
+    //
+    // At present fastints are used for [-0x80000000,0xffffffff] when
+    // they are encoded in shortest form (this is likely to change).
+    print('- array wrapped integer');
+    t([ 0x81, 0x11 ]);
+    t([ 0x81, 0x18, 0xff ]);
+    t([ 0x81, 0x1a, 0xfe, 0xdc, 0xba, 0x98 ]);
+    t([ 0x81, 0x1a, 0xff, 0xff, 0xff, 0xff ]);
+    t([ 0x81, 0x1b, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff ]);  // in range, non-shortest encoding
+    t([ 0x81, 0x1b, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00 ]);  // no longer in 32-bit range
+    t([ 0x81, 0x1b, 0x00, 0x00, 0x7e, 0xdc, 0xba, 0x98, 0x76, 0x54 ]);
+    t([ 0x81, 0x1b, 0x00, 0x00, 0x7f, 0xff, 0xff, 0xff, 0xff, 0xff ]);
+    t([ 0x81, 0x1b, 0x00, 0x00, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00 ]);  // no longer in fastint range
+    t([ 0x81, 0x1b, 0x00, 0x00, 0x80, 0xdc, 0xba, 0x98, 0x76, 0x54 ]);  // no longer in fastint range
+    t([ 0x81, 0x31 ]);
+    t([ 0x81, 0x38, 0xff ]);
+    t([ 0x81, 0x3a, 0x7f, 0xff, 0xff, 0xff ]);
+    t([ 0x81, 0x3a, 0x80, 0x00, 0x00, 0x00 ]);
+    t([ 0x81, 0x3a, 0xfe, 0xdc, 0xba, 0x98 ]);
+    t([ 0x81, 0x3b, 0x00, 0x00, 0x00, 0x00, 0x7f, 0xff, 0xff, 0xff ]);  // in range, non-shortest encoding
+    t([ 0x81, 0x3b, 0x00, 0x00, 0x00, 0x00, 0x80, 0x00, 0x00, 0x00 ]);  // no longer in 32-bit range
+    t([ 0x81, 0x3b, 0x00, 0x00, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00 ]);
+    t([ 0x81, 0x3b, 0x00, 0x00, 0x80, 0xdc, 0xba, 0x98, 0x76, 0x54 ]);
+
+    // Integer-compatible double.
+    //
+    // At present no fastint check (except for top level value).
+    //
+    // >>> cbor.dumps(17.0).encode('hex')
+    // 'fb4031000000000000'
+    print('- integer-compatible double');
+    t([ 0xfb, 0x40, 0x31, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 ]);
+    t([ 0x81, 0xfb, 0x40, 0x31, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 ]);
+
+    // Integer-compatible float or half-float.
+    //
+    // At present no fastint check (except for top level value).
+    print('- integer-compatible float');
+    t([ 0xfa, 0x42, 0xf6, 0x00, 0x00 ]);  // 123 as float
+    t([ 0x81, 0xfa, 0x42, 0xf6, 0x00, 0x00 ]);
+    print('- integer-compatible half-float');
+    t([ 0xf9, 0x57, 0xb0 ]);  // 123 as half-float
+    t([ 0x81, 0xf9, 0x57, 0xb0 ]);
+}
+
+try {
+    test();
+} catch (e) {
+    print(e.stack || e);
+}
diff --git a/tests/ecmascript/test-dev-fastint-basic.js b/tests/ecmascript/test-dev-fastint-basic.js
index 159bc347..99ea4c34 100644
--- a/tests/ecmascript/test-dev-fastint-basic.js
+++ b/tests/ecmascript/test-dev-fastint-basic.js
@@ -86,7 +86,7 @@ function printFastint(v) {
     }
 
     // The internal type tag depends on the duk_tval unpacked/packed layout.
-
+    // XXX: add to util.
     if (typeof Duktape !== 'object') {
         isfast = ' NOT-DUKTAPE';
     } else if (getValueInternalTag(true) >= 0xfff0) {
diff --git a/tests/perf/test-cbor-decode-fastints.js b/tests/perf/test-cbor-decode-fastints.js
new file mode 100644
index 00000000..84d5a048
--- /dev/null
+++ b/tests/perf/test-cbor-decode-fastints.js
@@ -0,0 +1,41 @@
+if (typeof print !== 'function') { print = console.log; }
+
+function build() {
+    var obj = [];
+
+    for (var i = 0; i < 1000; i++) {
+        obj.push(123);
+        obj.push(12);
+        obj.push(123);
+        obj.push(12);
+        obj.push(123);
+        obj.push(12);
+        obj.push(-123);
+        obj.push(-12);
+        obj.push(-123);
+        obj.push(-12);
+        obj.push(-123);
+        obj.push(-12);
+    }
+    return obj;
+}
+
+function test() {
+    var obj;
+    var buf;
+    var i;
+
+    obj = build();
+    buf = CBOR.encode(obj);
+
+    for (i = 0; i < 1e3; i++) {
+        void CBOR.decode(buf);
+    }
+}
+
+try {
+    test();
+} catch (e) {
+    print(e.stack || e);
+    throw e;
+}
diff --git a/tests/perf/test-cbor-decode-strings.js b/tests/perf/test-cbor-decode-strings.js
new file mode 100644
index 00000000..e143905d
--- /dev/null
+++ b/tests/perf/test-cbor-decode-strings.js
@@ -0,0 +1,30 @@
+if (typeof print !== 'function') { print = console.log; }
+
+function build() {
+    var obj = [];
+
+    for (var i = 0; i < 10000; i++) {
+        obj.push('foobar-' + i);
+    }
+    return obj;
+}
+
+function test() {
+    var obj;
+    var buf;
+    var i;
+
+    obj = build();
+    buf = CBOR.encode(obj);
+
+    for (i = 0; i < 1e3; i++) {
+        void CBOR.decode(buf);
+    }
+}
+
+try {
+    test();
+} catch (e) {
+    print(e.stack || e);
+    throw e;
+}
diff --git a/tests/perf/test-cbor-encode-double.js b/tests/perf/test-cbor-encode-double.js
new file mode 100644
index 00000000..60341777
--- /dev/null
+++ b/tests/perf/test-cbor-encode-double.js
@@ -0,0 +1,21 @@
+if (typeof print !== 'function') { print = console.log; }
+
+function test() {
+    var msg = [];
+    while (msg.length < 10000) {
+        msg[msg.length] = Math.PI;
+    }
+
+    // print(Duktape.enc('hex', CBOR.encode(msg)));
+
+    for (var i = 0; i < 1e3; i++) {
+        void CBOR.encode(msg);
+    }
+}
+
+try {
+    test();
+} catch (e) {
+    print(e.stack || e);
+    throw e;
+}
diff --git a/tests/perf/test-cbor-encode-float.js b/tests/perf/test-cbor-encode-float.js
new file mode 100644
index 00000000..df5dae93
--- /dev/null
+++ b/tests/perf/test-cbor-encode-float.js
@@ -0,0 +1,21 @@
+if (typeof print !== 'function') { print = console.log; }
+
+function test() {
+    var msg = [];
+    while (msg.length < 10000) {
+        msg[msg.length] = 100000.5;
+    }
+
+    // print(Duktape.enc('hex', CBOR.encode(msg)));
+
+    for (var i = 0; i < 1e3; i++) {
+        void CBOR.encode(msg);
+    }
+}
+
+try {
+    test();
+} catch (e) {
+    print(e.stack || e);
+    throw e;
+}
diff --git a/tests/perf/test-cbor-encode-half-float.js b/tests/perf/test-cbor-encode-half-float.js
new file mode 100644
index 00000000..0bd67f3b
--- /dev/null
+++ b/tests/perf/test-cbor-encode-half-float.js
@@ -0,0 +1,21 @@
+if (typeof print !== 'function') { print = console.log; }
+
+function test() {
+    var msg = [];
+    while (msg.length < 10000) {
+        msg[msg.length] = 1.5;
+    }
+
+    // print(Duktape.enc('hex', CBOR.encode(msg)));
+
+    for (var i = 0; i < 1e3; i++) {
+        void CBOR.encode(msg);
+    }
+}
+
+try {
+    test();
+} catch (e) {
+    print(e.stack || e);
+    throw e;
+}