Always specify the error expected to be raised

Using the `raise_error` matcher without providing a specific error or
message risks false positives, since `raise_error` will match when Ruby
raises a `NoMethodError`, `NameError` or `ArgumentError`, potentially
allowing the expectation to pass without even executing the method you
are intending to call.

spec/ruby-measurement/core_ext/string_spec.rb

@@ -14,12 +14,12 @@
 
     describe 'with valid quantity and invalid unit' do
       subject { '3 people' }
-      specify { expect { subject.to_measurement }.to raise_error }
+      specify { expect { subject.to_measurement }.to raise_error(ArgumentError) }
     end
 
     describe 'with invalid input' do
       subject { 'foobar' }
-      specify { expect { subject.to_measurement }.to raise_error }
+      specify { expect { subject.to_measurement }.to raise_error(ArgumentError) }
     end
   end
 
@@ -31,7 +31,7 @@
 
     describe 'with invalid unit' do
       subject { 'person' }
-      specify { expect { subject.to_unit }.to raise_error }
+      specify { expect { subject.to_unit }.to raise_error(ArgumentError) }
     end
   end
 end

spec/ruby-measurement/core_ext/symbol_spec.rb

@@ -9,7 +9,7 @@
 
     describe 'with invalid unit' do
       subject { :person }
-      specify { expect { subject.to_unit }.to raise_error }
+      specify { expect { subject.to_unit }.to raise_error(ArgumentError) }
     end
   end
 end

spec/ruby-measurement/measurement_spec.rb

@@ -38,13 +38,13 @@
 
     describe 'with invalid quantity' do
       it 'raises exception' do
-        expect { subject.new('hi') }.to raise_exception
+        expect { subject.new('hi') }.to raise_error(ArgumentError)
       end
     end
 
     describe 'with invalid unit' do
       it 'raises exception' do
-        expect { subject.new(3, :finklebaum) }.to raise_exception
+        expect { subject.new(3, :finklebaum) }.to raise_error(ArgumentError)
       end
     end
   end
@@ -146,7 +146,7 @@
       end
 
       it 'raises exception when undefined' do
-        expect { subject.parse('3 finklebaums') }.to raise_error
+        expect { subject.parse('3 finklebaums') }.to raise_error(ArgumentError)
       end
     end
   end
@@ -174,11 +174,11 @@
     end
 
     it 'raises exception if unit exists and is not convertable' do
-      expect { measurement.convert_to(:inches) }.to raise_error
+      expect { measurement.convert_to(:inches) }.to raise_error(ArgumentError)
     end
 
     it 'raises exception if unit does not exist' do
-      expect { measurement.convert_to(:finklebaum) }.to raise_error
+      expect { measurement.convert_to(:finklebaum) }.to raise_error(ArgumentError)
     end
   end
 
@@ -222,7 +222,7 @@
     it 'raises exception for incompatible units' do
       other = subject.new(4, :inches)
       expect(other.unit).to_not eq measurement.unit
-      expect { measurement + other }.to raise_error
+      expect { measurement + other }.to raise_error(ArgumentError)
     end
   end
 
@@ -256,7 +256,7 @@
     it 'raises exception for incompatible units' do
       other = subject.new(4, :inches)
       expect(other.unit).to_not eq measurement.unit
-      expect { measurement - other }.to raise_error
+      expect { measurement - other }.to raise_error(ArgumentError)
     end
   end
 
@@ -290,7 +290,7 @@
     it 'raises exception for incompatible units' do
       other = subject.new(4, :inches)
       expect(other.unit).to_not eq measurement.unit
-      expect { measurement * other }.to raise_error
+      expect { measurement * other }.to raise_error(ArgumentError)
     end
   end
 
@@ -324,7 +324,7 @@
     it 'raises exception for incompatible units' do
       other = subject.new(4, :inches)
       expect(other.unit).to_not eq measurement.unit
-      expect { measurement / other }.to raise_error
+      expect { measurement / other }.to raise_error(ArgumentError)
     end
   end
 
@@ -336,7 +336,7 @@
     end
 
     it 'raises exception for non-numeric values' do
-      expect { measurement ** subject.new(3) }.to raise_error
+      expect { measurement ** subject.new(3) }.to raise_error(ArgumentError)
     end
   end