diff --git a/src/modules/esl-popup/core/esl-popup-position.ts b/src/modules/esl-popup/core/esl-popup-position.ts
index 243068253..4a8a75037 100644
--- a/src/modules/esl-popup/core/esl-popup-position.ts
+++ b/src/modules/esl-popup/core/esl-popup-position.ts
@@ -1,5 +1,3 @@
-// TODO: make implemenatation immutable
-
 import {Rect} from '../../esl-utils/dom/rect';
 
 import type {Point} from '../../esl-utils/dom/point';
@@ -36,10 +34,18 @@ export interface PopupPositionConfig {
  * Checks that the position along the horizontal axis
  * @param position - name of position
  */
-export function isMajorAxisHorizontal(position: PositionType): boolean {
+export function isOnHorizontalAxis(position: PositionType): boolean {
   return ['left', 'right'].includes(position);
 }
 
+/**
+ * Checks whether the specified position corresponds to the starting side
+ * @param position - name of position
+ */
+function isStartingSide(position: PositionType): boolean {
+  return ['left', 'top'].includes(position);
+}
+
 /**
  * Calculates the position of the popup on the minor axis
  * @param cfg - popup position config
@@ -51,29 +57,41 @@ function calcPopupPositionByMinorAxis(cfg: PopupPositionConfig, centerPosition:
 }
 
 /**
- * TODO: optimize switch
  * Calculates Rect for given popup position config.
  * @param cfg - popup position config
  * */
 function calcPopupBasicRect(cfg: PopupPositionConfig): Rect {
-  let x = calcPopupPositionByMinorAxis(cfg, cfg.inner.cx, 'width');
-  let y = cfg.inner.y - cfg.element.height;
+  const {position, inner, element} = cfg;
+  let x = isOnHorizontalAxis(position) ? 0 : calcPopupPositionByMinorAxis(cfg, inner.cx, 'width');
+  let y = isOnHorizontalAxis(position) ? calcPopupPositionByMinorAxis(cfg, inner.cy, 'height') : 0;
   switch (cfg.position) {
     case 'left':
-      x = cfg.inner.x - cfg.element.width;
-      y = calcPopupPositionByMinorAxis(cfg, cfg.inner.cy, 'height');
+      x = inner.x - element.width;
       break;
     case 'right':
-      x = cfg.inner.right;
-      y = calcPopupPositionByMinorAxis(cfg, cfg.inner.cy, 'height');
+      x = inner.right;
       break;
     case 'bottom':
-      x = calcPopupPositionByMinorAxis(cfg, cfg.inner.cx, 'width');
-      y = cfg.inner.bottom;
+      y = inner.bottom;
+      break;
+    default:
+      y = inner.y - element.height;
       break;
   }
+  return new Rect(x, y, element.width, element.height);
+}
 
-  return new Rect(x, y, cfg.element.width, cfg.element.height);
+/**
+ * Calculates position for all sub-parts of popup for given popup position config.
+ * @param cfg - popup position config
+ * */
+function calcBasicPosition(cfg: PopupPositionConfig): PopupPositionValue {
+  const popup = calcPopupBasicRect(cfg);
+  const arrow = {
+    x: calcArrowPosition(cfg, 'width'),
+    y: calcArrowPosition(cfg, 'height'),
+  };
+  return {arrow, popup, placedAt: cfg.position};
 }
 
 /**
@@ -90,63 +108,59 @@ function getOppositePosition(position: PositionType): PositionType {
 }
 
 /**
- * TODO: move the actionsToFit definition outside the function and optimize
+ * Checks and updates popup and arrow positions to fit on major axis.
+ * @param cfg - popup position config
+ * @param value - current popup's position value
+ * @returns updated popup position value
+ * */
+function fitOnMajorAxis(cfg: PopupPositionConfig, value: PopupPositionValue): PopupPositionValue {
+  if (cfg.behavior !== 'fit' && cfg.behavior !== 'fit-major') return value;
+
+  const intersectionRatio = cfg.intersectionRatio[cfg.position] || 0;
+  const leftComparand = isStartingSide(cfg.position) ? value.popup[cfg.position] : cfg.outer[cfg.position];
+  const rightComparand = isStartingSide(cfg.position) ? cfg.outer[cfg.position] : value.popup[cfg.position];
+  const isRequireAdjusting = intersectionRatio > 0 || leftComparand < rightComparand;
+
+  return isRequireAdjusting ? adjustAlongMajorAxis(cfg, value) : value;
+}
+
+/**
  * Updates popup and arrow positions to fit on major axis.
  * @param cfg - popup position config
- * @param rect - popup position rect
- * @param arrow - arrow position value
+ * @param value - current popup's position value
+ * @returns updated popup position value
  * */
-function fitOnMajorAxis(cfg: PopupPositionConfig, rect: Rect): PositionType {
-  if (cfg.behavior !== 'fit' && cfg.behavior !== 'fit-on-major') return cfg.position;
-
-  let isMirrored = false;
-  const actionsToFit: Record<PositionType, () => void> = {
-    'bottom': () => {
-      if (cfg.intersectionRatio.bottom || cfg.outer.bottom < rect.bottom) {
-        rect.y = cfg.inner.y - cfg.element.height;
-        isMirrored = true;
-      }
-    },
-    'left': () => {
-      if (cfg.intersectionRatio.left || rect.x < cfg.outer.x) {
-        rect.x = cfg.inner.right;
-        isMirrored = true;
-      }
-    },
-    'right': () => {
-      if (cfg.intersectionRatio.right || cfg.outer.right < rect.right) {
-        rect.x = cfg.inner.x - cfg.element.width;
-        isMirrored = true;
-      }
-    },
-    'top': () => {
-      if (cfg.intersectionRatio.top || rect.y < cfg.outer.y) {
-        rect.y = cfg.inner.bottom;
-        isMirrored = true;
-      }
-    }
-  };
-  actionsToFit[cfg.position]();
+function adjustAlongMajorAxis(cfg: PopupPositionConfig, value: PopupPositionValue): PopupPositionValue {
+  let {popup, placedAt} = value;
+  let {x, y} = popup;
+  if (isStartingSide(cfg.position)) {
+    x = cfg.position === 'left' ? cfg.inner.right : x;
+    y = cfg.position === 'top' ? cfg.inner.bottom : y;
+  } else {
+    x = cfg.position === 'right' ? cfg.inner.x - popup.width : x;
+    y = cfg.position === 'bottom' ? cfg.inner.y - popup.height : y;
+  }
+  popup = new Rect(x, y, popup.width, popup.height);
+  placedAt = getOppositePosition(cfg.position);
 
-  return isMirrored ? getOppositePosition(cfg.position) : cfg.position;
+  return {...value, popup, placedAt};
 }
 
 /**
  * Calculates adjust for popup position to fit container bounds
- * @param elCoord - coordinate of the popup
- * @param outerCoord - coordinate of the outer border element
+ * @param diffCoord - distance between the popup and the outer (container) bounding
  * @param arrowCoord - coordinate of the arrow
  * @param arrowLimit - the limit value of the arrow coordinate
- * @param startingSide - is it starting side?
+ * @param isStart - is it starting side?
  * @returns adjustment value for the coordinates of the arrow and the popup
  */
-function adjustAlignmentBySide(elCoord: number, outerCoord: number, arrowCoord: number, arrowLimit: number, isStartingSide: boolean): number {
+function adjustAlignmentBySide(diffCoord: number, arrowCoord: number, arrowLimit: number, isStart: boolean): number {
   let arrowAdjust = 0;
 
-  if (isStartingSide ? elCoord < outerCoord : elCoord > outerCoord) {
-    arrowAdjust = elCoord - outerCoord;
+  if (isStart ? diffCoord < 0 : diffCoord > 0) {
+    arrowAdjust = diffCoord;
     const newCoord = arrowCoord + arrowAdjust;
-    if (isStartingSide ? newCoord < arrowLimit : newCoord > arrowLimit) {
+    if (isStart ? newCoord < arrowLimit : newCoord > arrowLimit) {
       arrowAdjust = 0;
     }
     /** It was decided that if the relative positions of the trigger and container
@@ -158,7 +172,7 @@ function adjustAlignmentBySide(elCoord: number, outerCoord: number, arrowCoord:
      *  Perhaps in the future, we should allow the user to choose the strategy.
      *
      * const func = isStartingSide ? Math.max : Math.min;
-     * arrowAdjust = func(elCoord - outerCoord, arrowLimit - arrowCoord);
+     * arrowAdjust = func(diffCoord, arrowLimit - arrowCoord);
      */
   }
 
@@ -168,13 +182,13 @@ function adjustAlignmentBySide(elCoord: number, outerCoord: number, arrowCoord:
 /**
  * Updates popup and arrow positions to fit on minor axis.
  * @param cfg - popup position config
- * @param rect - popup position rect
- * @param arrow - arrow position value
+ * @param value - current popup's position value
+ * @returns updated popup position value
  * */
-function fitOnMinorAxis(cfg: PopupPositionConfig, rect: Rect, arrow: Point): void {
-  if (cfg.behavior !== 'fit' && cfg.behavior !== 'fit-on-minor') return;
+function fitOnMinorAxis(cfg: PopupPositionConfig, value: PopupPositionValue): PopupPositionValue {
+  if (cfg.behavior !== 'fit' && cfg.behavior !== 'fit-minor') return value;
 
-  const isHorizontal = isMajorAxisHorizontal(cfg.position);
+  const isHorizontal = isOnHorizontalAxis(cfg.position);
   const start = isHorizontal ? 'y' : 'x';
   const end = isHorizontal ? 'bottom' : 'right';
   const dimension = isHorizontal ? 'height' : 'width';
@@ -182,23 +196,24 @@ function fitOnMinorAxis(cfg: PopupPositionConfig, rect: Rect, arrow: Point): voi
   if (cfg.outer[dimension] < cfg.element[dimension] ||  // cancel fit mode if the popup size is greater than the outer limiter size
       cfg.trigger[start] < cfg.outer[start] ||          // or the trigger is outside the outer limiting element
       cfg.trigger[end] > cfg.outer[end]
-  ) return;
+  ) return value;
 
-  let coordAdjust = 0;
+  const {popup, arrow} = value;
   // check the starting side of the axis
   let arrowLimit = cfg.marginArrow;
-  coordAdjust = adjustAlignmentBySide(rect[start], cfg.outer[start], arrow[start], arrowLimit, true);
+  let coordAdjust = adjustAlignmentBySide(popup[start] - cfg.outer[start], arrow[start], arrowLimit, true);
   if (coordAdjust) {
-    rect[start] -= coordAdjust;
+    popup[start] -= coordAdjust;
     arrow[start] += coordAdjust;
   }
   // check the final side of the axis
   arrowLimit += calcUsableSizeForArrow(cfg, dimension);
-  coordAdjust = adjustAlignmentBySide(rect[end], cfg.outer[end], arrow[start], arrowLimit, false);
+  coordAdjust = adjustAlignmentBySide(popup[end] - cfg.outer[end], arrow[start], arrowLimit, false);
   if (coordAdjust) {
-    rect[start] -= coordAdjust;
+    popup[start] -= coordAdjust;
     arrow[start] += coordAdjust;
   }
+  return {...value, popup, arrow};
 }
 
 /**
@@ -224,19 +239,5 @@ function calcArrowPosition(cfg: PopupPositionConfig, dimensionName: 'height' | '
  * @param cfg - popup position config
  * */
 export function calcPopupPosition(cfg: PopupPositionConfig): PopupPositionValue {
-  const popup = calcPopupBasicRect(cfg);
-  const arrow = {
-    x: calcArrowPosition(cfg, 'width'),
-    y: calcArrowPosition(cfg, 'height'),
-    position: cfg.position
-  };
-
-  const placedAt = fitOnMajorAxis(cfg, popup);
-  fitOnMinorAxis(cfg, popup, arrow);
-
-  return {
-    popup,
-    placedAt,
-    arrow
-  };
+  return fitOnMinorAxis(cfg, fitOnMajorAxis(cfg, calcBasicPosition(cfg)));
 }
diff --git a/src/modules/esl-popup/core/esl-popup.ts b/src/modules/esl-popup/core/esl-popup.ts
index 7f269f3ac..485d8610b 100644
--- a/src/modules/esl-popup/core/esl-popup.ts
+++ b/src/modules/esl-popup/core/esl-popup.ts
@@ -11,7 +11,7 @@ import {getViewportRect} from '../../esl-utils/dom/window';
 import {parseBoolean, parseNumber, toBooleanAttribute} from '../../esl-utils/misc/format';
 import {copyDefinedKeys} from '../../esl-utils/misc/object';
 import {ESLIntersectionTarget, ESLIntersectionEvent} from '../../esl-event-listener/core/targets/intersection.target';
-import {calcPopupPosition, isMajorAxisHorizontal} from './esl-popup-position';
+import {calcPopupPosition, isOnHorizontalAxis} from './esl-popup-position';
 import {ESLPopupPlaceholder} from './esl-popup-placeholder';
 
 import type {ESLToggleableActionParams} from '../../esl-toggleable/core';
@@ -309,7 +309,7 @@ export class ESLPopup extends ESLToggleable {
       return;
     }
 
-    const isHorizontal = isMajorAxisHorizontal(this.position);
+    const isHorizontal = isOnHorizontalAxis(this.position);
     const checkIntersection = (isMajorAxis: boolean, intersectionRatio: number): void => {
       if (isMajorAxis && intersectionRatio < INTERSECTION_LIMIT_FOR_ADJACENT_AXIS) this.hide();
     };
@@ -421,12 +421,11 @@ export class ESLPopup extends ESLToggleable {
     // set popup position
     this.style.left = `${popup.x}px`;
     this.style.top = `${popup.y}px`;
+    if (!this.$arrow) return;
     // set arrow position
-    if (this.$arrow) {
-      const isHorizontal = isMajorAxisHorizontal(this.position);
-      this.$arrow.style.left = isHorizontal ? '' : `${arrow.x}px`;
-      this.$arrow.style.top = isHorizontal ? `${arrow.y}px` : '';
-    }
+    const isHorizontal = isOnHorizontalAxis(this.position);
+    this.$arrow.style.left = isHorizontal ? '' : `${arrow.x}px`;
+    this.$arrow.style.top = isHorizontal ? `${arrow.y}px` : '';
   }
 }
 
diff --git a/src/modules/esl-popup/test/esl-popup-position.behaviour-fit-major.test.ts b/src/modules/esl-popup/test/esl-popup-position.behaviour-fit-major.test.ts
new file mode 100644
index 000000000..5850579c3
--- /dev/null
+++ b/src/modules/esl-popup/test/esl-popup-position.behaviour-fit-major.test.ts
@@ -0,0 +1,94 @@
+import {calcPopupPosition} from '../core/esl-popup-position';
+import {Rect} from '../../esl-utils/dom';
+
+import type {PopupPositionConfig, PopupPositionValue} from '../core/esl-popup-position';
+
+describe('ESLPopup position: calcPopupPosition(): behavior set to fit-major', () => {
+  const arrow = new Rect(0, 0, 30, 30);
+  const popup = new Rect(0, 0, 300, 200);
+  const trigger = new Rect(500, 500, 20, 20);
+  const container = new Rect(0, 0, 1000, 1000);
+  const intersectionRatio = {top: 0, left: 0, right: 0, bottom: 0};
+  const cfgRef = {
+    behavior: 'fit-major',
+    position: 'top',
+    marginArrow: 7,
+    offsetArrowRatio: 0,
+    intersectionRatio,
+    arrow,
+    element: popup,
+    inner: trigger.grow(10),
+    outer: container,
+    trigger
+  } as PopupPositionConfig;
+
+  const expectedRef = {
+    arrow: {x: 7, y: 7},
+    placedAt: 'top',
+    popup
+  };
+
+  describe('should flip to the opposite position:', () => {
+    test('when there is a lack of space at the top', () => {
+      const cfg = {...cfgRef, position: 'top', outer: container.shift(0, 400)} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(488, 530);
+      expected.placedAt = 'bottom';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when there is a lack of space at the left', () => {
+      const cfg = {...cfgRef, position: 'left', outer: container.shift(400, 0)} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(530, 488);
+      expected.placedAt = 'right';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when there is a lack of space at the bottom', () => {
+      const cfg = {...cfgRef, position: 'bottom', outer: container.shift(0, -400)} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(488, 290);
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when there is a lack of space at the right', () => {
+      const cfg = {...cfgRef, position: 'right', outer: container.shift(-400, 0)} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(190, 488);
+      expected.placedAt = 'left';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when the activator is crossing the top edge of the container', () => {
+      const cfg = {...cfgRef, position: 'top', intersectionRatio: {top: 0.5, left: 0, right: 0, bottom: 0}} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(488, 530);
+      expected.placedAt = 'bottom';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when the activator is crossing the left edge of the container', () => {
+      const cfg = {...cfgRef, position: 'left', intersectionRatio: {top: 0, left: 0.5, right: 0, bottom: 0}} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(530, 488);
+      expected.placedAt = 'right';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when the activator is crossing the bottom edge of the container', () => {
+      const cfg = {...cfgRef, position: 'bottom', intersectionRatio: {top: 0, left: 0, right: 0, bottom: 0.5}} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(488, 290);
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when the activator is crossing the right edge of the container', () => {
+      const cfg = {...cfgRef, position: 'right', intersectionRatio: {top: 0, left: 0, right: 0.5, bottom: 0}} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(190, 488);
+      expected.placedAt = 'left';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+  });
+});
diff --git a/src/modules/esl-popup/test/esl-popup-position.behaviour-fit-minor.test.ts b/src/modules/esl-popup/test/esl-popup-position.behaviour-fit-minor.test.ts
new file mode 100644
index 000000000..e8c215d34
--- /dev/null
+++ b/src/modules/esl-popup/test/esl-popup-position.behaviour-fit-minor.test.ts
@@ -0,0 +1,137 @@
+import {calcPopupPosition} from '../core/esl-popup-position';
+import {Rect} from '../../esl-utils/dom';
+
+import type {PopupPositionConfig, PopupPositionValue} from '../core/esl-popup-position';
+
+describe('ESLPopup position: calcPopupPosition(): behavior set to fit-minor', () => {
+  const arrow = new Rect(0, 0, 30, 30);
+  const popup = new Rect(0, 0, 300, 200);
+  const trigger = new Rect(500, 500, 20, 20);
+  const container = new Rect(0, 0, 1000, 1000);
+  const intersectionRatio = {top: 0, left: 0, right: 0, bottom: 0};
+  const cfgRef = {
+    behavior: 'fit-minor',
+    position: 'top',
+    marginArrow: 20,
+    offsetArrowRatio: 0.5,
+    intersectionRatio,
+    arrow,
+    element: popup,
+    inner: trigger.grow(10),
+    outer: container,
+    trigger
+  } as PopupPositionConfig;
+
+  const expectedRef = {
+    arrow: {x: 135, y: 85},
+    placedAt: 'top',
+    popup
+  };
+
+  describe('should adjust the position by moving to:', () => {
+    test('left when there is a lack of space on the right side in the top position', () => {
+      const cfg = {...cfgRef, position: 'top', outer: container.shift(-440, 0)} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.arrow = {x: 235, y: 85};
+      expected.popup = popup.shift(260, 290);
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('right when there is a lack of space on the left side in the top position', () => {
+      const cfg = {...cfgRef, position: 'top', outer: container.shift(440, 0)} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.arrow = {x: 55, y: 85};
+      expected.popup = popup.shift(440, 290);
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('left when there is a lack of space on the right side in the bottom position', () => {
+      const cfg = {...cfgRef, position: 'bottom', outer: container.shift(-440, 0)} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.arrow = {x: 235, y: 85};
+      expected.popup = popup.shift(260, 530);
+      expected.placedAt = 'bottom';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('right when there is a lack of space on the left side in the bottom position', () => {
+      const cfg = {...cfgRef, position: 'bottom', outer: container.shift(440, 0)} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.arrow = {x: 55, y: 85};
+      expected.popup = popup.shift(440, 530);
+      expected.placedAt = 'bottom';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+  });
+
+  describe('should not adjust the position in case:', () => {
+    test('when the popup size is greater than the outer limiter size', () => {
+      const narrowContainer = trigger.grow(50);
+      const cfg = {...cfgRef, position: 'top', outer: narrowContainer} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(360, 290);
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    describe('when the popup has a position on the vertical axis', () => {
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(360, 290);
+      test('when the trigger is outside of the outer limiting element by the own left edge', () => {
+        const cfg = {...cfgRef, position: 'top', outer: container.shift(-510, 0)} as PopupPositionConfig;
+        expect(calcPopupPosition(cfg)).toEqual(expected);
+      });
+
+      test('when the trigger is outside of the outer limiting element by the own right edge', () => {
+        const cfg = {...cfgRef, position: 'top', outer: container.shift(510, 0)} as PopupPositionConfig;
+        expect(calcPopupPosition(cfg)).toEqual(expected);
+      });
+    });
+
+    describe('when the popup has a position on the horizontal axis', () => {
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(530, 410);
+      expected.placedAt = 'right';
+      test('when the trigger is outside of the outer limiting element by the own top edge', () => {
+        const cfg = {...cfgRef, position: 'right', outer: container.shift(0, -510)} as PopupPositionConfig;
+        expect(calcPopupPosition(cfg)).toEqual(expected);
+      });
+
+      test('when the trigger is outside of the outer limiting element by the own right edge', () => {
+        const cfg = {...cfgRef, position: 'right', outer: container.shift(0, 510)} as PopupPositionConfig;
+        expect(calcPopupPosition(cfg)).toEqual(expected);
+      });
+    });
+
+    describe('when there is a lack of space for position adjustment on the horizontal axis:', () => {
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(360, 530);
+      expected.placedAt = 'bottom';
+
+      test('when it is required to move to the left', () => {
+        const cfg = {...cfgRef, position: 'bottom', outer: container.shift(-460, 0)} as PopupPositionConfig;
+        expect(calcPopupPosition(cfg)).toEqual(expected);
+      });
+
+      test('when it is required to move to the right', () => {
+        const cfg = {...cfgRef, position: 'bottom', outer: container.shift(480, 0)} as PopupPositionConfig;
+        expect(calcPopupPosition(cfg)).toEqual(expected);
+      });
+    });
+
+    describe('when there is a lack of space for position adjustment on the vertical axis:', () => {
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(530, 410);
+      expected.placedAt = 'right';
+
+      test('when it is required to move to the top', () => {
+        const cfg = {...cfgRef, position: 'right', outer: container.shift(0, -460)} as PopupPositionConfig;
+        expect(calcPopupPosition(cfg)).toEqual(expected);
+      });
+
+      test('when it is required to move to the bottom', () => {
+        const cfg = {...cfgRef, position: 'right', outer: container.shift(0, 480)} as PopupPositionConfig;
+        expect(calcPopupPosition(cfg)).toEqual(expected);
+      });
+    });
+  });
+});
diff --git a/src/modules/esl-popup/test/esl-popup-position.behaviour-fit.test.ts b/src/modules/esl-popup/test/esl-popup-position.behaviour-fit.test.ts
new file mode 100644
index 000000000..28f15c85b
--- /dev/null
+++ b/src/modules/esl-popup/test/esl-popup-position.behaviour-fit.test.ts
@@ -0,0 +1,202 @@
+import {calcPopupPosition} from '../core/esl-popup-position';
+import {Rect} from '../../esl-utils/dom';
+
+import type {PopupPositionConfig, PopupPositionValue} from '../core/esl-popup-position';
+
+describe('ESLPopup position: calcPopupPosition(): behavior set to fit-major', () => {
+  const arrow = new Rect(0, 0, 30, 30);
+  const popup = new Rect(0, 0, 300, 200);
+  const trigger = new Rect(500, 500, 20, 20);
+  const container = new Rect(0, 0, 1000, 1000);
+  const intersectionRatio = {top: 0, left: 0, right: 0, bottom: 0};
+  const cfgRef = {
+    behavior: 'fit',
+    position: 'top',
+    marginArrow: 20,
+    offsetArrowRatio: 0.5,
+    intersectionRatio,
+    arrow,
+    element: popup,
+    inner: trigger.grow(10),
+    outer: container,
+    trigger
+  } as PopupPositionConfig;
+
+  const expectedRef = {
+    arrow: {x: 135, y: 85},
+    placedAt: 'top',
+    popup
+  };
+
+  describe('should flip to the opposite position:', () => {
+    test('when there is a lack of space at the top', () => {
+      const cfg = {...cfgRef, position: 'top', outer: container.shift(0, 400)} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(360, 530);
+      expected.placedAt = 'bottom';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when there is a lack of space at the left', () => {
+      const cfg = {...cfgRef, position: 'left', outer: container.shift(400, 0)} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(530, 410);
+      expected.placedAt = 'right';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when there is a lack of space at the bottom', () => {
+      const cfg = {...cfgRef, position: 'bottom', outer: container.shift(0, -400)} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(360, 290);
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when there is a lack of space at the right', () => {
+      const cfg = {...cfgRef, position: 'right', outer: container.shift(-400, 0)} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(190, 410);
+      expected.placedAt = 'left';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when the activator is crossing the top edge of the container', () => {
+      const cfg = {...cfgRef, position: 'top', intersectionRatio: {top: 0.5, left: 0, right: 0, bottom: 0}} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(360, 530);
+      expected.placedAt = 'bottom';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when the activator is crossing the left edge of the container', () => {
+      const cfg = {...cfgRef, position: 'left', intersectionRatio: {top: 0, left: 0.5, right: 0, bottom: 0}} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(530, 410);
+      expected.placedAt = 'right';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when the activator is crossing the bottom edge of the container', () => {
+      const cfg = {...cfgRef, position: 'bottom', intersectionRatio: {top: 0, left: 0, right: 0, bottom: 0.5}} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(360, 290);
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when the activator is crossing the right edge of the container', () => {
+      const cfg = {...cfgRef, position: 'right', intersectionRatio: {top: 0, left: 0, right: 0.5, bottom: 0}} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(190, 410);
+      expected.placedAt = 'left';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+  });
+
+  describe('should adjust the position by moving to:', () => {
+    test('left when there is a lack of space on the right side in the top position', () => {
+      const cfg = {...cfgRef, position: 'top', outer: container.shift(-440, 0)} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.arrow = {x: 235, y: 85};
+      expected.popup = popup.shift(260, 290);
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('right when there is a lack of space on the left side in the top position', () => {
+      const cfg = {...cfgRef, position: 'top', outer: container.shift(440, 0)} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.arrow = {x: 55, y: 85};
+      expected.popup = popup.shift(440, 290);
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('left when there is a lack of space on the right side in the bottom position', () => {
+      const cfg = {...cfgRef, position: 'bottom', outer: container.shift(-440, 0)} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.arrow = {x: 235, y: 85};
+      expected.popup = popup.shift(260, 530);
+      expected.placedAt = 'bottom';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('right when there is a lack of space on the left side in the bottom position', () => {
+      const cfg = {...cfgRef, position: 'bottom', outer: container.shift(440, 0)} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.arrow = {x: 55, y: 85};
+      expected.popup = popup.shift(440, 530);
+      expected.placedAt = 'bottom';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+  });
+
+  describe('should not adjust the position in case:', () => {
+    test('when the popup size is greater than the outer limiter size', () => {
+      const narrowContainer = trigger.grow(50);
+      const cfg = {...cfgRef, position: 'top', outer: narrowContainer} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(360, 530);
+      expected.placedAt = 'bottom';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    describe('when the popup has a position on the vertical axis', () => {
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(360, 290);
+      test('when the trigger is outside of the outer limiting element by the own left edge', () => {
+        const cfg = {...cfgRef, position: 'top', outer: container.shift(-510, 0)} as PopupPositionConfig;
+        expect(calcPopupPosition(cfg)).toEqual(expected);
+      });
+
+      test('when the trigger is outside of the outer limiting element by the own right edge', () => {
+        const cfg = {...cfgRef, position: 'top', outer: container.shift(510, 0)} as PopupPositionConfig;
+        expect(calcPopupPosition(cfg)).toEqual(expected);
+      });
+    });
+
+    describe('when the popup has a position on the horizontal axis', () => {
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(530, 410);
+      expected.placedAt = 'right';
+      test('when the trigger is outside of the outer limiting element by the own top edge', () => {
+        const cfg = {...cfgRef, position: 'right', outer: container.shift(0, -510)} as PopupPositionConfig;
+        expect(calcPopupPosition(cfg)).toEqual(expected);
+      });
+
+      test('when the trigger is outside of the outer limiting element by the own right edge', () => {
+        const cfg = {...cfgRef, position: 'right', outer: container.shift(0, 510)} as PopupPositionConfig;
+        expect(calcPopupPosition(cfg)).toEqual(expected);
+      });
+    });
+
+    describe('when there is a lack of space for position adjustment on the horizontal axis:', () => {
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(360, 530);
+      expected.placedAt = 'bottom';
+
+      test('when it is required to move to the left', () => {
+        const cfg = {...cfgRef, position: 'bottom', outer: container.shift(-460, 0)} as PopupPositionConfig;
+        expect(calcPopupPosition(cfg)).toEqual(expected);
+      });
+
+      test('when it is required to move to the right', () => {
+        const cfg = {...cfgRef, position: 'bottom', outer: container.shift(480, 0)} as PopupPositionConfig;
+        expect(calcPopupPosition(cfg)).toEqual(expected);
+      });
+    });
+
+    describe('when there is a lack of space for position adjustment on the vertical axis:', () => {
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(530, 410);
+      expected.placedAt = 'right';
+
+      test('when it is required to move to the top', () => {
+        const cfg = {...cfgRef, position: 'right', outer: container.shift(0, -460)} as PopupPositionConfig;
+        expect(calcPopupPosition(cfg)).toEqual(expected);
+      });
+
+      test('when it is required to move to the bottom', () => {
+        const cfg = {...cfgRef, position: 'right', outer: container.shift(0, 480)} as PopupPositionConfig;
+        expect(calcPopupPosition(cfg)).toEqual(expected);
+      });
+    });
+  });
+});
diff --git a/src/modules/esl-popup/test/esl-popup-position.behaviour-none.test.ts b/src/modules/esl-popup/test/esl-popup-position.behaviour-none.test.ts
new file mode 100644
index 000000000..ee4ca56b0
--- /dev/null
+++ b/src/modules/esl-popup/test/esl-popup-position.behaviour-none.test.ts
@@ -0,0 +1,88 @@
+import {calcPopupPosition} from '../core/esl-popup-position';
+import {Rect} from '../../esl-utils/dom';
+
+import type {PopupPositionConfig, PopupPositionValue} from '../core/esl-popup-position';
+
+describe('ESLPopup position: calcPopupPosition(): behavior set to none', () => {
+  const arrow = new Rect(0, 0, 30, 30);
+  const popup = new Rect(0, 0, 300, 200);
+  const trigger = new Rect(500, 500, 20, 20);
+  const container = new Rect(0, 0, 1000, 1000);
+  const cfgRef = {
+    behavior: 'none',
+    position: 'top',
+    marginArrow: 7,
+    offsetArrowRatio: 0,
+    intersectionRatio: {top: 0, left: 0, right: 0, bottom: 0},
+    arrow,
+    element: popup,
+    inner: trigger.grow(10),
+    outer: container,
+    trigger
+  } as PopupPositionConfig;
+
+  const expectedRef = {
+    arrow: {x: 7, y: 7},
+    placedAt: 'top',
+    popup
+  };
+
+  describe('should calc position without adjustments:', () => {
+    test('when the popup placed at the top', () => {
+      const cfg = {...cfgRef, position: 'top'} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(488, 290);
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when the popup placed at the left', () => {
+      const cfg = {...cfgRef, position: 'left'} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(190, 488);
+      expected.placedAt = 'left';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when the popup placed at the bottom', () => {
+      const cfg = {...cfgRef, position: 'bottom'} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(488, 530);
+      expected.placedAt = 'bottom';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when the popup placed at the right', () => {
+      const cfg = {...cfgRef, position: 'right'} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(530, 488);
+      expected.placedAt = 'right';
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+  });
+
+  describe('should calc arrow position:', () => {
+
+    test('when arrow at the start edge', () => {
+      const cfg = {...cfgRef, offsetArrowRatio: 0} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.popup = popup.shift(488, 290);
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when arrow at the end edge', () => {
+      const cfg = {...cfgRef, offsetArrowRatio: 1} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.arrow = {x: 263, y: 163};
+      expected.popup = popup.shift(232, 290);
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+
+    test('when arrow at the middle', () => {
+      const cfg = {...cfgRef, offsetArrowRatio: 0.5} as PopupPositionConfig;
+      const expected = Object.assign({}, expectedRef) as PopupPositionValue;
+      expected.arrow = {x: 135, y: 85};
+      expected.popup = popup.shift(360, 290);
+      expect(calcPopupPosition(cfg)).toEqual(expected);
+    });
+  });
+});
diff --git a/src/modules/esl-popup/test/esl-popup-position.test.ts b/src/modules/esl-popup/test/esl-popup-position.test.ts
new file mode 100644
index 000000000..af549a2a4
--- /dev/null
+++ b/src/modules/esl-popup/test/esl-popup-position.test.ts
@@ -0,0 +1,21 @@
+import {isOnHorizontalAxis} from '../core/esl-popup-position';
+
+describe('ESLPopup position: tests', () => {
+  describe('isMajorAxisHorizontal() function:', () => {
+    test('should return true for left position', () => {
+      expect(isOnHorizontalAxis('left')).toBe(true);
+    });
+
+    test('should return true for right position', () => {
+      expect(isOnHorizontalAxis('right')).toBe(true);
+    });
+
+    test('should return false for top position', () => {
+      expect(isOnHorizontalAxis('top')).toBe(false);
+    });
+
+    test('should return false for bottom position', () => {
+      expect(isOnHorizontalAxis('bottom')).toBe(false);
+    });
+  });
+});
diff --git a/src/modules/esl-utils/dom/test/window.test.ts b/src/modules/esl-utils/dom/test/window.test.ts
new file mode 100644
index 000000000..590d10925
--- /dev/null
+++ b/src/modules/esl-utils/dom/test/window.test.ts
@@ -0,0 +1,57 @@
+import {Rect} from '../rect';
+import {getWindow, getWindowRect, getViewportRect} from '../window';
+
+describe('getWindow() function:', () => {
+  test('should return window when the passed node is null', () => {
+    const node = null as any;
+    expect(getWindow(node)).toBe(window);
+  });
+
+  test('should return window when the passed node is window', () => {
+    const node = window;
+    expect(getWindow(node)).toBe(window);
+  });
+
+  test('should return window for the passed node', () => {
+    const node = document.createElement('div');
+    expect(getWindow(node)).toBe(window);
+  });
+
+  test('should return window when the passed node is document element', () => {
+    const node = document.createElement('div').ownerDocument;
+    expect(getWindow(node)).toBe(window);
+  });
+
+  test('should return window as fallback value when the passed node has ownerDocument without defaultView', () => {
+    const node = {ownerDocument: {}} as Node;
+    expect(getWindow(node)).toBe(window);
+  });
+});
+
+describe('getWindowRect() function:', () => {
+  test('should return window rect', () => {
+    expect(getWindowRect()).toEqual(new Rect(0, 0, 1024, 768));
+  });
+});
+
+describe('getViewportRect() function:', () => {
+  const clientWidthOriginal = document.documentElement.clientWidth;
+  const clientHeightOriginal = document.documentElement.clientHeight;
+
+  beforeAll(() => {
+    const scrollbarWidth = 17;
+    const clientWidth = window.innerWidth - scrollbarWidth;
+    const clientHeight = window.innerHeight - scrollbarWidth;
+    Object.defineProperty(document.documentElement, 'clientWidth', {value: clientWidth, configurable: true});
+    Object.defineProperty(document.documentElement, 'clientHeight', {value: clientHeight, configurable: true});
+  });
+
+  afterAll(() => {
+    Object.defineProperty(document.documentElement, 'clientWidth', {value: clientWidthOriginal, configurable: true});
+    Object.defineProperty(document.documentElement, 'clientHeight', {value: clientHeightOriginal, configurable: true});
+  });
+
+  test('should return viewport rect', () => {
+    expect(getViewportRect()).toEqual(new Rect(0, 0, 1007, 751));
+  });
+});