Add missing specs

spec/std/big/big_decimal_spec.cr

@@ -172,6 +172,11 @@ describe BigDecimal do
   describe "#round" do
     {% for sign in %w[+ -] %}
       context "(with {{sign.id}} sign)" do
+        it "returns self if digits are equal or more than significant digits" do
+          BigDecimal.new("{{sign.id}}2.5").round(1)
+            .should eq(BigDecimal.new(BigInt.new({{sign.id}}25), 1))
+        end
+
         it "rounds :up" do
           BigDecimal.new("{{sign.id}}2.1").round(0, :up)
             .should eq(BigDecimal.new(BigInt.new({{sign.id}}3)))
@@ -198,6 +203,16 @@ describe BigDecimal do
           BigDecimal.new("{{sign.id}}2.5").round(0, :half_even)
             .should eq(BigDecimal.new(BigInt.new({{sign.id}}2)))
         end
+
+        it "rounds :ceil" do
+          BigDecimal.new("{{sign.id}}2.5").round(0, :ceil)
+            .should eq(BigDecimal.new(BigInt.new({{sign.id}}{{sign == "+" ? 3 : 2}})))
+        end
+
+        it "rounds :floor" do
+          BigDecimal.new("{{sign.id}}2.5").round(0, :floor)
+            .should eq(BigDecimal.new(BigInt.new({{sign.id}}{{sign == "-" ? 3 : 2}})))
+        end
       end
     {% end %}
   end