diff --git a/Magical8bitPlug2.jucer b/Magical8bitPlug2.jucer
index a4db363..a8b4e52 100644
--- a/Magical8bitPlug2.jucer
+++ b/Magical8bitPlug2.jucer
@@ -10,6 +10,10 @@
               pluginDesc="8bit sound generator 2nd ver. by YMCK" displaySplashScreen="1"
               jucerFormatVersion="1" version="1.0.1">
   <MAINGROUP id="tlJ5Jv" name="Magical8bitPlug2">
+    <GROUP id="{90CFFF6B-201B-9373-6BE8-DDF2F136949F}" name="Tests">
+      <FILE id="WZca8g" name="EnvelopeParserTest.h" compile="0" resource="0"
+            file="Source/EnvelopeParserTest.h"/>
+    </GROUP>
     <GROUP id="{05934500-901F-8317-27DC-7E17FC00833D}" name="View">
       <GROUP id="{68A7410F-88F9-C9D8-8A37-6A70F269BBCC}" name="BaseComponents">
         <FILE id="lBYKKS" name="CheckBoxComponent.cpp" compile="1" resource="0"
diff --git a/Source/EnvelopeParserTest.h b/Source/EnvelopeParserTest.h
new file mode 100644
index 0000000..4e5e443
--- /dev/null
+++ b/Source/EnvelopeParserTest.h
@@ -0,0 +1,90 @@
+/*
+  ==============================================================================
+
+    EnvelopeParserTest.h
+    Created: 13 Aug 2021 6:14:32pm
+    Author:  除村武志
+
+  ==============================================================================
+*/
+
+#pragma once
+#include "../JuceLibraryCode/JuceHeader.h"
+#include "FrameSequence.h"
+#include "FrameSequenceParser.h"
+#include "FrameSequenceParseErrors.h"
+
+class EnvelopeParserTest : public UnitTest {
+
+public:
+    EnvelopeParserTest() : UnitTest("Custom Envelope Parser Test") {}
+    
+    void runTest() override
+    {
+        FrameSequenceParser parser;
+                
+        beginTest ("No repeat");
+        String input1 = "aaa"; // At this phase it doesn't matter if it contains numbers or not
+        auto result1 = parser.findSegment(input1);
+        expect(result1.repeatStartIndex == SegmentIndexes::NONE);
+        expect(result1.repeatEndIndex == SegmentIndexes::NONE);
+        expect(result1.releaseBlockIndex == SegmentIndexes::NONE);
+
+        beginTest ("With repeat, no release");
+        String input2 = "aa[bbb]";
+        auto result2 = parser.findSegment(input2);
+        expect(result2.repeatStartIndex == 3);
+        expect(result2.repeatEndIndex == 6);
+        expect(result2.releaseBlockIndex == SegmentIndexes::NONE);
+        
+        beginTest ("Repeat segment starts from the top");
+        String input3 = "[aaa]";
+        auto result3 = parser.findSegment(input3);
+        expect(result3.repeatStartIndex == 1);
+        expect(result3.repeatEndIndex == 4);
+        expect(result3.releaseBlockIndex == SegmentIndexes::NONE);
+
+        beginTest ("No repeat, with release");
+        String input4 = "aaa|bbbb";
+        auto result4 = parser.findSegment(input4);
+        expect(result4.repeatStartIndex == SegmentIndexes::NONE);
+        expect(result4.repeatEndIndex == 3); // It doesn't repeat, but it has to keep the last index of pre-release segment
+        expect(result4.releaseBlockIndex == 4);
+        
+        beginTest ("Release segment without pre-release segment");
+        String input5 = "|bbbb";
+        auto result5 = parser.findSegment(input5);
+        expect(result5.repeatStartIndex == SegmentIndexes::NONE);
+        expect(result5.repeatEndIndex == 0); // This results in an immediate transition to Release Phase
+        expect(result5.releaseBlockIndex == 1);
+
+        beginTest ("Repeat and release (no pre-repeat)");
+        String input6 = "[aaa]|bbbb";
+        auto result6 = parser.findSegment(input6);
+        expect(result6.repeatStartIndex == 1);
+        expect(result6.repeatEndIndex == 4);
+        expect(result6.releaseBlockIndex == 6);
+
+        beginTest ("Repeat and release (with pre-repeat)");
+        String input7 = "aaa[bbb]|cccc";
+        auto result7 = parser.findSegment(input7);
+        expect(result7.repeatStartIndex == 4);
+        expect(result7.repeatEndIndex == 7);
+        expect(result7.releaseBlockIndex == 9);
+
+        beginTest ("Empty repeat section");
+        String input8 = "aaa[]|cccc";
+        auto result8 = parser.findSegment(input8);
+        expect(result8.repeatStartIndex == 4);
+        expect(result8.repeatEndIndex == 4);
+        expect(result8.releaseBlockIndex == 6);
+
+        beginTest ("Empty release section");
+        String input9 = "aaa[bbb]|";
+        auto result9 = parser.findSegment(input9);
+        expect(result9.repeatStartIndex == 4);
+        expect(result9.repeatEndIndex == 7);
+        expect(result9.releaseBlockIndex == 9);
+
+    }
+};
diff --git a/Source/FrameSequenceParser.cpp b/Source/FrameSequenceParser.cpp
index e7c855e..713d440 100644
--- a/Source/FrameSequenceParser.cpp
+++ b/Source/FrameSequenceParser.cpp
@@ -224,7 +224,7 @@ std::vector<int> FrameSequenceParser::parseSegment (const String& input,
     return retval;
 }
 
-FrameSequenceParser::SegmentIndexes FrameSequenceParser::findSegment(const String& input) {
+SegmentIndexes FrameSequenceParser::findSegment(const String& input) {
     int releaseBlockIndex = -1;
     int repeatStartIndex = -1;
     int repeatEndIndex = -1;
@@ -359,112 +359,11 @@ FrameSequence FrameSequenceParser::parse (const String& input,
     //
     // Overall structure
     //
+    SegmentIndexes si = findSegment(trimmed);
 
-    int releaseBlockIndex = -1;
-    int repeatStartIndex = -1;
-    int repeatEndIndex = -1;
-    int openBracketCount = 0;
-    int closeBracketCount = 0;
-
-    // loop by character
-    for (int i = 0; i < trimmed.length(); i++)
-    {
-        if (trimmed[i] == '|')  // found "|":
-        {
-            if (releaseBlockIndex >= 0)
-            {
-                //   if releaseBlockIndex is already determined: Duplication Error
-                *error = kParseErrorDuplicatedReleaseDelimiter;
-                return fs;
-            }
-
-            //            if(repeatStartIndex >= 0) {
-            //                //   if appeard before "[" or  "]": Repetition After Release Error
-            //                throw new FrameSequenceParseException(TRANS("You cannot repeat in release phase"), true);
-            //            }
-            //   set releaseBlockIndex
-            releaseBlockIndex = i + 1;
-
-            if (repeatEndIndex < 0)
-            {
-                // if "]" is omitted: Also set repeatEndIndex
-                repeatEndIndex = i;
-            }
-        }
-
-        if (trimmed[i] == '[')  /// found "[":
-        {
-            openBracketCount++;
-
-            if (openBracketCount > 1)
-            {
-                //   Duplication Error
-                *error = kParseErrorDuplicatedOpenBracket;
-                return fs;
-            }
-
-            if (releaseBlockIndex >= 0)
-            {
-                //   if repeat end is already defined: Repetition After Release Error
-                *error = kParseErrorRepeatingInReleaseBlock;
-                return fs;
-            }
-
-            if (repeatEndIndex >= 0)
-            {
-                //   if repeat end is already defined: Repetition After Release Error
-                *error = kParseErrorDuplicatedOpenBracket;
-                return fs;
-            }
-
-            //   set repeatStartIndex
-            repeatStartIndex = i + 1;
-        }
-
-        if (trimmed[i] == ']')  // found "]":
-        {
-            closeBracketCount++;
-
-            if (closeBracketCount > 1)
-            {
-                //    Duplication Error
-                *error = kParseErrorDuplicatedCloseBracket;
-                return fs;
-            }
-
-            if (repeatStartIndex < 0)
-            {
-                //   if repeatStartIndex hasn't set: Syntax Error
-                *error = kParseErrorUnmatchingCloseBracket;
-                return fs;
-            }
-
-            if (releaseBlockIndex >= 0)
-            {
-                //   if repeat end is already defined: Repetition After Release Error
-                *error = kParseErrorRepeatingInReleaseBlock;
-                return fs;
-            }
-
-            repeatEndIndex = i;
-        }
-    }
-
-    //    if (releaseBlockIndex < 0) { // "|" didn't explicitly specified
-    //        releaseBlockIndex = trimmed.length();
-    //    }
-
-    if (openBracketCount != closeBracketCount)
-    {
-        *error = kParseErrorUnmatchingBracketNumber;
-        return fs;
-    }
-
-    if (releaseBlockIndex - repeatEndIndex > 1)
-    {
-        //        throw new FrameSequenceParseException(TRANS("Elements between repeat block and release block will be ignored"), false);
-        // FiXME: non-fatal exceptionをどう扱うか
-    }
+    int releaseBlockIndex = si.releaseBlockIndex;
+    int repeatStartIndex = si.repeatStartIndex;
+    int repeatEndIndex = si.repeatEndIndex;
 
     // Just for convenience
     bool hasRelease = (releaseBlockIndex >= 0);
diff --git a/Source/FrameSequenceParser.h b/Source/FrameSequenceParser.h
index 15ca5d5..dccc77a 100644
--- a/Source/FrameSequenceParser.h
+++ b/Source/FrameSequenceParser.h
@@ -13,6 +13,15 @@
 #include "FrameSequence.h"
 #include "FrameSequenceParseErrors.h"
 
+struct SegmentIndexes {
+    static const int NONE = -1;
+    
+    int releaseBlockIndex = NONE;
+    int repeatStartIndex = NONE;
+    int repeatEndIndex = NONE;
+    ParseError error;
+};
+
 struct FrameSequenceParser
 {
     /*
@@ -23,15 +32,6 @@ struct FrameSequenceParser
     /*
      Semantically private (leave them open for unit testing)
      */
-    struct SegmentIndexes {
-        const int NONE = -1;
-        
-        int releaseBlockIndex = NONE;
-        int repeatStartIndex = NONE;
-        int repeatEndIndex = NONE;
-        ParseError error;
-    };
-
     std::vector<int> parseSlope (const String& input,
                                  int minValue,
                                  int maxValue,
diff --git a/Source/PluginProcessor.cpp b/Source/PluginProcessor.cpp
index 270ea3b..27b41f7 100644
--- a/Source/PluginProcessor.cpp
+++ b/Source/PluginProcessor.cpp
@@ -14,6 +14,7 @@
 #include "TriangleVoice.h"
 #include "NoiseVoice.h"
 #include "FrameSequenceParseErrors.h"
+#include "EnvelopeParserTest.h"
 
 //==============================================================================
 Magical8bitPlug2AudioProcessor::Magical8bitPlug2AudioProcessor()
@@ -114,7 +115,7 @@ Magical8bitPlug2AudioProcessor::Magical8bitPlug2AudioProcessor()
         std::make_unique<AudioParameterBool> ("isPitchSequenceEnabled_raw", "Enabled", false),
         std::make_unique<AudioParameterBool> ("isDutySequenceEnabled_raw", "Enabled", false),
         std::make_unique<AudioParameterChoice> ("pitchSequenceMode_raw", "Mode", StringArray ({"Coarse", "Fine"}), 0)
-}
+    }
   )
 , settingRefs (&parameters)
 #ifndef JucePlugin_PreferredChannelConfigurations
@@ -132,6 +133,12 @@ Magical8bitPlug2AudioProcessor::Magical8bitPlug2AudioProcessor()
 
     setupVoice();
     synth.addSound (new GenericSound());
+    
+#if JUCE_DEBUG
+    EnvelopeParserTest test;
+    UnitTestRunner runner;
+    runner.runAllTests();
+#endif
 }
 
 Magical8bitPlug2AudioProcessor::~Magical8bitPlug2AudioProcessor()