diff --git a/src/main/kotlin/com/memoizr/assertk/AbstractAssertBuilder.kt b/src/main/kotlin/com/memoizr/assertk/AbstractAssertBuilder.kt
index 87fc53f..a8b6795 100644
--- a/src/main/kotlin/com/memoizr/assertk/AbstractAssertBuilder.kt
+++ b/src/main/kotlin/com/memoizr/assertk/AbstractAssertBuilder.kt
@@ -22,7 +22,7 @@ abstract class AbstractAssertBuilder<S : AbstractAssertBuilder<S, A>, A : Any>(a
     }
 
     @Suppress("UNUSED_PARAMETER")
-    inline infix fun <reified R : Any> isInstance(bar: InstanceMatcher<R>): S {
+    inline infix fun <reified R : Any> isInstance(bar: InstanceMatcher<out R>): S {
         assertion.isInstanceOf(R::class.java)
         return myself
     }
diff --git a/src/main/kotlin/com/memoizr/assertk/DoubleAssert.kt b/src/main/kotlin/com/memoizr/assertk/DoubleAssert.kt
index e4c3a28..ad679c2 100644
--- a/src/main/kotlin/com/memoizr/assertk/DoubleAssert.kt
+++ b/src/main/kotlin/com/memoizr/assertk/DoubleAssert.kt
@@ -3,6 +3,22 @@ package com.memoizr.assertk
 import org.assertj.core.api.AbstractDoubleAssert
 import org.assertj.core.api.Assertions
 
+infix fun Double.isLessThan(expected: Double): DoubleAssert = expect that this isLessThan expected
+infix fun Double.isLessThanOrEqualTo(expected: Double): DoubleAssert = expect that this isLessThanOrEqualTo expected
+infix fun Double.isGreaterThan(expected: Double): DoubleAssert = expect that this isGreaterThan expected
+infix fun Double.isGreaterThanOrEqualTo(expected: Double): DoubleAssert = expect that this isGreaterThanOrEqualTo  expected
+infix fun Double.isBetween(expected: ClosedRange<Double>): DoubleAssert = expect that this isBetween expected
+infix fun Double.isStrictlyBetween(expected: ClosedRange<Double>): DoubleAssert = expect that this isStrictlyBetween  expected
+infix fun Double.isCloseTo(expected: Double): DoubleAssert.Close = expect that this isCloseTo expected
+infix fun Double.isEqualTo(expected: Double): DoubleAssert = expect that this isEqualTo expected
+infix fun Double.isNotEqualTo(expected: Double): DoubleAssert = expect that this isNotEqualTo expected
+infix fun Double.isInstance(expected: AbstractAssertBuilder.InstanceMatcher<Double>): DoubleAssert = expect that this isInstance expected
+infix fun Double.is_(expected: NumberSelector): DoubleAssert = expect that this _is expected
+infix fun Double.is_(expected: ObjectSelector): DoubleAssert = expect that this _is expected
+infix fun Double._is(expected: NumberSelector): DoubleAssert = expect that this _is expected
+infix fun Double._is(expected: ObjectSelector): DoubleAssert = expect that this _is expected
+infix fun Double.describedAs(description: String): DoubleAssert = expect that this describedAs description
+
 class DoubleAssert internal constructor(
         subjectUnderTest: Double?,
         override val assertion: AbstractDoubleAssert<*> = Assertions.assertThat(subjectUnderTest)) :
@@ -42,6 +58,8 @@ class DoubleAssert internal constructor(
         return Close(expected, assertion, this)
     }
 
+    infix fun is_(expected: NumberSelector): DoubleAssert = _is(expected)
+
     infix fun _is(expected: NumberSelector): DoubleAssert {
         when (expected) {
             zero -> assertion.isZero()
diff --git a/src/main/kotlin/com/memoizr/assertk/ObjectAssert.kt b/src/main/kotlin/com/memoizr/assertk/ObjectAssert.kt
index a803d2e..2cc3020 100644
--- a/src/main/kotlin/com/memoizr/assertk/ObjectAssert.kt
+++ b/src/main/kotlin/com/memoizr/assertk/ObjectAssert.kt
@@ -3,6 +3,13 @@ package com.memoizr.assertk
 import org.assertj.core.api.AbstractObjectAssert
 import org.assertj.core.api.Assertions
 
+infix fun <A: Any> A.isEqualTo(expected: A): ObjectAssert<A> = expect that this isEqualTo expected
+infix fun <A: Any> A.isNotEqualTo(expected: A): ObjectAssert<A> = expect that this isNotEqualTo expected
+infix fun <A: Any> A.is_(expected: ObjectSelector): ObjectAssert<A> = expect that this _is expected
+infix fun <A: Any> A.describedAs(description: String): ObjectAssert<A> = expect that this describedAs description
+inline infix fun <reified A: Any> A.isInstance(expected: AbstractAssertBuilder.InstanceMatcher<out A>): ObjectAssert<A> =
+        expect.that(this).isInstance(expected)
+
 class ObjectAssert<A : Any> internal constructor(
         actual: A?,
         override val assertion: AbstractObjectAssert<*, A> = Assertions.assertThat(actual)) :
diff --git a/src/test/kotlin/com/memoizr/assertk/Double assert test.kt b/src/test/kotlin/com/memoizr/assertk/Double assert test.kt
index d2bc24d..ea93971 100644
--- a/src/test/kotlin/com/memoizr/assertk/Double assert test.kt	
+++ b/src/test/kotlin/com/memoizr/assertk/Double assert test.kt	
@@ -10,7 +10,7 @@ class `Double assert test` {
     lateinit var mockAssertion: AbstractDoubleAssert<*>
     @Suppress("UNCHECKED_CAST")
     val _expect = object : AssertionHook {
-        override fun that(subjectUnderTest: Double?): DoubleAssert {
+            override fun that(subjectUnderTest: Double?): DoubleAssert {
             val spy: AbstractDoubleAssert<*> = spy(Assertions.assertThat(subjectUnderTest))
             mockAssertion = spy
             return DoubleAssert(subjectUnderTest, mockAssertion)
@@ -28,81 +28,120 @@ class `Double assert test` {
     private val one = 1.0
     private val negativeOne = -one
 
+    @Test
+    fun isEqualTo() {
+        three isEqualTo three andCanBe chained
+    }
+
+    @Test
+    fun isNotEqualTo() {
+        three isNotEqualTo four andCanBe chained
+    }
+
+    @Test
+    fun isInstance() {
+        three isInstance of<Double>() andCanBe chained
+    }
+
+    @Test
+    fun is_() {
+        three is_ notNull andCanBe chained
+        three is_ notNegative andCanBe chained
+    }
+
+    @Test
+    fun describedAs() {
+        three describedAs "foo" andCanBe chained
+    }
+
     @Test
     fun isLessThan() {
         _expect that three isLessThan four andCanBe chained
+        three isLessThan four andCanBe chained
         verify.isLessThan(four)
     }
 
     @Test
     fun isLessThanOrEqualTo() {
         _expect that four isLessThanOrEqualTo four andCanBe chained
+        four isLessThanOrEqualTo four andCanBe chained
         verify.isLessThanOrEqualTo(four)
     }
 
     @Test
     fun isGreaterThan() {
         _expect that five isGreaterThan four andCanBe chained
+        five isGreaterThan four andCanBe chained
         verify.isGreaterThan(four)
     }
 
     @Test
     fun isGreaterThanOrEqualTo() {
         _expect that four isGreaterThanOrEqualTo four andCanBe chained
+        four isGreaterThanOrEqualTo four andCanBe chained
         verify.isGreaterThanOrEqualTo(four)
     }
 
     @Test
     fun isBetween() {
         _expect that four isBetween (three..five) andCanBe chained
+        four isBetween (three..five) andCanBe chained
         verify.isBetween(three, five)
     }
 
     @Test
     fun isStrictlyBetween() {
         _expect that four isStrictlyBetween (three..five) andCanBe chained
+        four isStrictlyBetween (three..five) andCanBe chained
         verify.isStrictlyBetween(three, five)
     }
 
     @Test
     fun `isCloseTo within`() {
         _expect that four isCloseTo three withinOffset one andCanBe chained
+        four isCloseTo three withinOffset one andCanBe chained
         verify.isCloseTo(three, Assertions.within(one))
     }
 
     @Test
     fun `isCloseTo percentage int`() {
         _expect that three isCloseTo four withinPercentage 25 andCanBe chained
+        three isCloseTo four withinPercentage 25 andCanBe chained
         verify.isCloseTo(four, Assertions.withinPercentage(25))
     }
 
     @Test
     fun `isCloseTo percentage double`() {
         _expect that three isCloseTo four withinPercentage 25.3 andCanBe chained
+        three isCloseTo four withinPercentage 25.3 andCanBe chained
         verify.isCloseTo(four, Assertions.withinPercentage(25.3))
     }
 
     @Test
     fun `isCloseTo percentage float`() {
         _expect that three isCloseTo four withinPercentage 25f andCanBe chained
+        three isCloseTo four withinPercentage 25f andCanBe chained
         verify.isCloseTo(four, Assertions.withinPercentage(25))
     }
 
     @Test
     fun isZero() {
         _expect that 0.0 _is zero andCanBe chained
+        0.0 _is zero andCanBe chained
         verify.isZero()
     }
 
     @Test
     fun isNotZero() {
         _expect that one _is notZero andCanBe chained
+        one _is notZero andCanBe chained
         verify.isNotZero()
     }
 
     @Test
     fun isPositive() {
         _expect that one _is positive andCanBe chained
+        one _is positive andCanBe chained
         verify.isPositive()
     }
 
@@ -110,18 +149,21 @@ class `Double assert test` {
     @Test
     fun isNotPositive() {
         _expect that negativeOne _is notPositive andCanBe chained
+        negativeOne _is notPositive andCanBe chained
         verify.isNotPositive()
     }
 
     @Test
     fun isNegative() {
         _expect that negativeOne _is negative andCanBe chained
+        negativeOne _is negative andCanBe chained
         verify.isNegative()
     }
 
     @Test
     fun isNotNegative() {
         _expect that one _is notNegative andCanBe chained
+        one _is notNegative andCanBe chained
         verify.isNotNegative()
     }
 
diff --git a/src/test/kotlin/com/memoizr/assertk/Object assert test.kt b/src/test/kotlin/com/memoizr/assertk/Object assert test.kt
index dc00a7e..ce7feeb 100644
--- a/src/test/kotlin/com/memoizr/assertk/Object assert test.kt	
+++ b/src/test/kotlin/com/memoizr/assertk/Object assert test.kt	
@@ -6,6 +6,10 @@ import org.assertj.core.api.AbstractObjectAssert
 import org.assertj.core.api.Assertions
 import org.junit.Test
 
+interface FooBars
+object A : FooBars
+object B
+
 class `Object assert test` {
     val nullObject: Any? = null
 
@@ -19,6 +23,32 @@ class `Object assert test` {
         }
     }
 
+    @Test
+    fun isEqualTo() {
+        Unit isEqualTo Unit
+    }
+
+    @Test
+    fun isNotEqualTo() {
+        A isNotEqualTo B
+    }
+
+    @Test
+    fun isInstance() {
+        expect that (A as FooBars) isInstance of<A>()
+        (A as FooBars) isInstance of<A>()
+    }
+
+    @Test
+    fun is_() {
+        A is_ notNull
+    }
+
+    @Test
+    fun describedAs() {
+        A describedAs "foo"
+    }
+
     @Test
     fun `isEqualTo performs logical equality`() {
         _expect that Unit isEqualTo Unit